friedkiwi/ibm-information-center
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
0332907f0f
ibm-information-center/dist/eclipse/plugins/i5OS.ic.db2_5.4.0.1/rbafzmstch2bas.htm

1130 lines
64 KiB
HTML
Raw Normal View History

Add readme and dist folders
2024-04-02 14:02:31 +00:00
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US" xml:lang="en-us">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="dc.language" scheme="rfc1766" content="en-us" />
<!-- All rights reserved. Licensed Materials Property of IBM -->
<!-- US Government Users Restricted Rights -->
<!-- Use, duplication or disclosure restricted by -->
<!-- GSA ADP Schedule Contract with IBM Corp. -->
<meta name="dc.date" scheme="iso8601" content="2005-09-19" />
<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
<meta name="security" content="public" />
<meta name="Robots" content="index,follow"/>
<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
<meta name="keywords" content="assignments and comparisons,
SQL (Structured Query Language), description, operation, basic operations in SQL,
assignment operation, assignment, comparison operation, data types,
compatibility, rules, compatibility rules, comparison, null value in SQL,
assignments, numeric, truncation of numbers, numbers,
conversion of numbers in SQL, scale of data, scale and precision,
conversion of numbers, string, strings, binary string, binary strings,
character string, character strings, graphic string, graphic strings,
*NOCNULRQD precompiler option, truncated during assignment,
double-byte character, not truncated by assignments, shift-in character,
in string assignments, mixed data, *CNULRQD precompiler option,
conversion rule for comparisons, conversion rules,
DBCS (double-byte character set), double-byte character set (DBCS),
date and time values, date and time, DATE, TIME, TIMESTAMP, DataLink, Row ID,
distinct type, LOB Locators, comparisons, comparisons in SQL,
character data string, distinct type values" />
<title>Assignments and comparisons</title>
<link rel="stylesheet" type="text/css" href="ibmidwb.css" />
<link rel="stylesheet" type="text/css" href="ic.css" />
</head>
<body>
<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
<a name="ch2bas"></a>
<h2 id="ch2bas"><a href="rbafzmst02.htm#ToC_139">Assignments and comparisons</a></h2><a id="idx427" name="idx427"></a><a id="idx428" name="idx428"></a><a id="idx429" name="idx429"></a><a id="idx430" name="idx430"></a><a id="idx431" name="idx431"></a><a id="idx432" name="idx432"></a><a id="idx433" name="idx433"></a><a id="idx434" name="idx434"></a><a id="idx435" name="idx435"></a><a id="idx436" name="idx436"></a><a id="idx437" name="idx437"></a><a id="idx438" name="idx438"></a>
<p>The basic operations of SQL are assignment and comparison. Assignment operations
are performed during the execution of CALL, INSERT, UPDATE, FETCH, SELECT,
SET variable, and VALUES INTO statements. Comparison operations are performed
during the execution of statements that include predicates and other language
elements such as MAX, MIN, DISTINCT, GROUP BY, and ORDER BY.</p>
<p>The basic rule for both operations is that the data type of the operands
involved must be compatible. The compatibility rule also applies to UNION,
EXCEPT, INTERSECT, concatenation, CASE expressions, and the CONCAT, VALUE,
COALESCE, IFNULL, MIN, and MAX scalar functions. The compatibility matrix
is as follows:</p>
<a name="wq147"></a>
<table id="wq147" width="100%" summary="" border="1" frame="hsides" rules="rows">
<caption>Table 15. Data Type Compatibility</caption>
<thead valign="bottom">
<tr>
<th id="wq148" width="20%" align="left" valign="bottom">
<div class="lines">&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
Operands<br />
&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
</div></th>
<th id="wq149" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Binary&nbsp;Integer<br />
</div></th>
<th id="wq150" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Decimal&nbsp;Number&nbsp;<br />
</div></th>
<th id="wq151" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Floating&nbsp;Point<br />
</div></th>
<th id="wq152" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Character&nbsp;String<br />
</div></th>
<th id="wq153" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Graphic&nbsp;String<br />
</div></th>
<th id="wq154" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Binary&nbsp;String<br />
</div></th>
<th id="wq155" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Date<br />
</div></th>
<th id="wq156" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Time<br />
</div></th>
<th id="wq157" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Timestamp<br />
</div></th>
<th id="wq158" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;DataLink<br />
</div></th>
<th id="wq159" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Row&nbsp;ID<br />
</div></th>
<th id="wq160" width="6%" align="left" valign="middle">
<div class="lines">&nbsp;&nbsp;Distinct&nbsp;Type<br />
</div></th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left" valign="top" headers="wq148">Binary Integer</td>
<td align="center" valign="top" headers="wq149">Yes</td>
<td align="center" valign="top" headers="wq150">Yes</td>
<td align="center" valign="top" headers="wq151">Yes</td>
<td align="center" valign="top" headers="wq152">Yes</td>
<td align="center" valign="top" headers="wq153">1</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Decimal Number <sup>5</sup></td>
<td align="center" valign="top" headers="wq149">Yes</td>
<td align="center" valign="top" headers="wq150">Yes</td>
<td align="center" valign="top" headers="wq151">Yes</td>
<td align="center" valign="top" headers="wq152">Yes</td>
<td align="center" valign="top" headers="wq153">1</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Floating Point</td>
<td align="center" valign="top" headers="wq149">Yes</td>
<td align="center" valign="top" headers="wq150">Yes</td>
<td align="center" valign="top" headers="wq151">Yes</td>
<td align="center" valign="top" headers="wq152">Yes</td>
<td align="center" valign="top" headers="wq153">1</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Character String</td>
<td align="center" valign="top" headers="wq149">Yes</td>
<td align="center" valign="top" headers="wq150">Yes</td>
<td align="center" valign="top" headers="wq151">Yes</td>
<td align="center" valign="top" headers="wq152">Yes</td>
<td align="center" valign="top" headers="wq153">1</td>
<td align="center" valign="top" headers="wq154">2</td>
<td align="center" valign="top" headers="wq155">3</td>
<td align="center" valign="top" headers="wq156">3</td>
<td align="center" valign="top" headers="wq157">3</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Graphic String</td>
<td align="center" valign="top" headers="wq149">1</td>
<td align="center" valign="top" headers="wq150">1</td>
<td align="center" valign="top" headers="wq151">1</td>
<td align="center" valign="top" headers="wq152">1</td>
<td align="center" valign="top" headers="wq153">Yes</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">1&nbsp;3</td>
<td align="center" valign="top" headers="wq156">1&nbsp;3</td>
<td align="center" valign="top" headers="wq157">1&nbsp;3</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Binary String</td>
<td align="center" valign="top" headers="wq149">No</td>
<td align="center" valign="top" headers="wq150">No</td>
<td align="center" valign="top" headers="wq151">No</td>
<td align="center" valign="top" headers="wq152">2</td>
<td align="center" valign="top" headers="wq153">No</td>
<td align="center" valign="top" headers="wq154">Yes</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Date</td>
<td align="center" valign="top" headers="wq149">No</td>
<td align="center" valign="top" headers="wq150">No</td>
<td align="center" valign="top" headers="wq151">No</td>
<td align="center" valign="top" headers="wq152">3</td>
<td align="center" valign="top" headers="wq153">1&nbsp;3</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">Yes</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Time</td>
<td align="center" valign="top" headers="wq149">No</td>
<td align="center" valign="top" headers="wq150">No</td>
<td align="center" valign="top" headers="wq151">No</td>
<td align="center" valign="top" headers="wq152">3</td>
<td align="center" valign="top" headers="wq153">1&nbsp;3</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">Yes</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Timestamp</td>
<td align="center" valign="top" headers="wq149">No</td>
<td align="center" valign="top" headers="wq150">No</td>
<td align="center" valign="top" headers="wq151">No</td>
<td align="center" valign="top" headers="wq152">3</td>
<td align="center" valign="top" headers="wq153">1&nbsp;3</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">Yes</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">DataLink</td>
<td align="center" valign="top" headers="wq149">No</td>
<td align="center" valign="top" headers="wq150">No</td>
<td align="center" valign="top" headers="wq151">No</td>
<td align="center" valign="top" headers="wq152">No</td>
<td align="center" valign="top" headers="wq153">No</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">6</td>
<td align="center" valign="top" headers="wq159">No</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Row ID</td>
<td align="center" valign="top" headers="wq149">No</td>
<td align="center" valign="top" headers="wq150">No</td>
<td align="center" valign="top" headers="wq151">No</td>
<td align="center" valign="top" headers="wq152">No</td>
<td align="center" valign="top" headers="wq153">No</td>
<td align="center" valign="top" headers="wq154">No</td>
<td align="center" valign="top" headers="wq155">No</td>
<td align="center" valign="top" headers="wq156">No</td>
<td align="center" valign="top" headers="wq157">No</td>
<td align="center" valign="top" headers="wq158">No</td>
<td align="center" valign="top" headers="wq159">7</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq148">Distinct Type</td>
<td align="center" valign="top" headers="wq149">4</td>
<td align="center" valign="top" headers="wq150">4</td>
<td align="center" valign="top" headers="wq151">4</td>
<td align="center" valign="top" headers="wq152">4</td>
<td align="center" valign="top" headers="wq153">4</td>
<td align="center" valign="top" headers="wq154">4</td>
<td align="center" valign="top" headers="wq155">4</td>
<td align="center" valign="top" headers="wq156">4</td>
<td align="center" valign="top" headers="wq157">4</td>
<td align="center" valign="top" headers="wq158">4</td>
<td align="center" valign="top" headers="wq159">4</td>
<td align="center" valign="top" headers="wq160">4</td>
</tr>
<tr>
<td colspan="13" align="left" valign="top" headers="wq148 wq149 wq150 wq151 wq152 wq153 wq154 wq155 wq156 wq157 wq158 wq159 wq160">
<a name="wq161"></a>
<div class="notetitle" id="wq161">Notes:</div>
<div class="notebody">
<ol type="1">
<li>Only UCS-2 and UTF-16 strings are compatible.</li>
<li>All character strings, even those with FOR BIT DATA, are not compatible
with binary strings except during assignments to or from variables or parameter
markers. In this case, FOR BIT DATA character strings and binary strings are
considered compatible and any padding is performed based on the data type
of the target. For example, when assigning a FOR BIT DATA column value to
a fixed-length binary variable, any necessary padding uses a pad byte of X'00'.</li>
<li>The datetime values and strings are not compatible in concatenation or
in the CONCAT scalar function.</li>
<li>A value with a distinct type is comparable only to a value that is defined
with the same distinct type. In general, the database manager supports assignments between
a distinct type value and its source data type. For additional information,
see <a href="rbafzmstch2bas.htm#udtasgn">Distinct type assignments</a>.</li>
<li>Decimal refers to both packed and zoned decimal.</li>
<li>A DataLink operand can only be assigned to another DataLink operand and
cannot be compared to any data type.</li>
<li>A ROWID operand can only be assigned to another ROWID operand and cannot
be compared to any data type.</li></ol></div></td>
</tr>
</tbody>
</table><a id="idx439" name="idx439"></a>
<p>A basic rule for assignment operations is that a null value cannot be assigned
to: </p>
<ul>
<li>a column that cannot contain null values</li>
<li>a host variable that does not have an associated indicator variable</li>
<li>a Java&trade; host variable that is a primitive type.</li></ul><p class="indatacontent"> See <a href="rbafzmstch2refvar.htm#ch2host">References to host variables</a> for a discussion of indicator variables.</p>
<p>For any comparison that involves null values, see the description of the
comparison operation for information about the specific handling of null
values.</p>
<a name="numass"></a>
<h3 id="numass"><a href="rbafzmst02.htm#ToC_140">Numeric assignments</a></h3><a id="idx440" name="idx440"></a><a id="idx441" name="idx441"></a><a id="idx442" name="idx442"></a>
<p>The basic rule for numeric assignments is that the whole part of a decimal
or integer number cannot be truncated. If necessary, the fractional part of
a decimal number is truncated.</p>
<p>An error occurs if: </p>
<ul>
<li>Truncation of the whole part of the number occurs on assignment to a column
or a parameter of a function or procedure</li>
<li>Truncation of the whole part of the number occurs on assignment to a host
variable that does not have an indicator variable</li></ul>
<p>A warning occurs if: </p>
<ul class="simple">
<li>Truncation of the whole part of the number occurs on assignment to a host
variable with an indicator variable. In this case, the number is not assigned
to the host variable and the indicator variable is set to negative 2.</li></ul>
<a name="wq163"></a>
<div class="notetitle" id="wq163">Note:</div>
<div class="notebody">Decimal refers to both packed and zoned decimal.</div>
<p></p>
<a name="wq164"></a>
<div class="notetitle" id="wq164">Note:</div>
<div class="notebody">When fetching decimal data from a file that was <span class="italic">not</span> created by an SQL CREATE TABLE statement, a decimal field may contain
data that is not valid. In this case, the data will be returned as stored,
without any warning or error message being issued. A table that is created
by the SQL CREATE TABLE statement does not allow decimal data that is not
valid.</div>
<a name="wq165"></a>
<h4 id="wq165">Decimal or integer to floating-point</h4>
<p>Floating-point numbers are approximations of real numbers. Hence, when
a decimal or integer number is assigned to a floating-point column or variable,
the result may not be identical to the original number.</p>
<p>The approximation is more accurate if the receiving column or variable
is defined as double precision (64 bits) rather than single precision (32
bits).</p>
<a name="wq166"></a>
<h4 id="wq166">Floating-point or decimal to integer</h4>
<p>When a floating-point or decimal number is assigned to a binary integer
column or variable, the number is converted, if necessary, to the precision
and the scale of the target. If the scale of the target is zero, the fractional
part of the number is lost. The necessary number of leading zeros is added
or eliminated, and the necessary number of trailing zeros in the fractional
part of the number is added or eliminated.</p>
<a name="wq167"></a>
<h4 id="wq167">Decimal to decimal</h4><a id="idx443" name="idx443"></a><a id="idx444" name="idx444"></a>
<p>When a decimal number is assigned to a decimal column or variable, the
number is converted, if necessary, to the precision and the scale of the target.
The necessary number of leading zeros is added or eliminated, and the necessary
number of trailing zeros in the fractional part of the number is added or
eliminated.</p>
<a name="wq168"></a>
<h4 id="wq168">Integer to decimal</h4>
<p>When an integer is assigned to a decimal column or variable, the number
is converted first to a temporary decimal number and then, if necessary, to
the precision and scale of the target. If the scale of the integer is zero,
the precision of the temporary decimal number is 5,0 for a small integer,
11,0 for a large integer, or 19,0 for a big integer.</p>
<a name="wq169"></a>
<h4 id="wq169">Floating-point to decimal</h4>
<p>When a floating-point number is assigned to a decimal column or variable,
the number is first converted to a temporary decimal number of precision 63
and then, if necessary, truncated to the precision and scale of the target.
In this conversion, the number is rounded (using floating-point arithmetic)
to a precision of 63 decimal digits. As a result, a number less than 0.5*10<sup>-63</sup> is reduced to 0. The scale is given the largest
possible value that allows the whole part of the number to be represented
without loss of significance.</p>
<a name="wq170"></a>
<h4 id="wq170">Assignments to COBOL and RPG integers</h4>
<p>Assignment to COBOL and RPG small or large integer host variables takes
into account any scale specified for the host variable. However, assignment
to integer host variables uses the full size of the integer. Thus, the value
placed in the COBOL data item or RPG field may be larger than the maximum
precision specified for the host variable.</p>
<p>In COBOL, for example, if COL1 contains a value of 12345, the statements: </p>
<pre class="xmp"> 01 A PIC S9999 BINARY.
EXEC SQL <span class="bold">SELECT</span> COL1
<span class="bold">INTO</span> :A
<span class="bold">FROM</span> TABLEX
END-EXEC.</pre><p class="indatacontent"> result in the value 12345 being placed in <tt class="xph">A</tt>,
even though <tt class="xph">A</tt> has been defined with only 4 digits.</p>
<p>Notice that the following COBOL statement: </p>
<pre class="xmp"> MOVE 12345 TO A.</pre><p class="indatacontent"> results
in 2345 being placed in <tt class="xph">A</tt>. <a id="idx445" name="idx445"></a></p>
<a name="wq171"></a>
<h4 id="wq171">Strings to numeric</h4>
<p>When a string is assigned to a numeric data type, it is converted to the
target numeric data type using the rules for a CAST specification. For more
information, see <a href="rbafzmstdatetimearith.htm#cast">CAST specification</a>.</p>
<a name="charas"></a>
<h3 id="charas"><a href="rbafzmst02.htm#ToC_148">String assignments</a></h3><a id="idx446" name="idx446"></a><a id="idx447" name="idx447"></a>
<p>There are two types of string assignments:</p>
<ul>
<li><span class="italic">Storage assignment</span> is when a value is assigned
to a column or a parameter of a function or stored procedure.</li>
<li><span class="italic">Retrieval assignment</span> is when a value is assigned
to a variable.</li></ul>
<a name="wq172"></a>
<h4 id="wq172">Binary string assignments</h4><a id="idx448" name="idx448"></a><a id="idx449" name="idx449"></a>
<a name="wq173"></a>
<h5 id="wq173">Storage assignment</h5>
<p>The basic rule is that the length of a string assigned to a column or parameter
of a function or procedure must not be greater than the length attribute of
the column or parameter. If the string is longer than the length attribute
of that column or parameter, a error is returned. Trailing hexadecimal zeroes
(X'00') are normally included in the length of the string. For storage assignments,
however, trailing hexadecimal zeroes are not included in the length of the
string.</p>
<p>When a string is assigned to a fixed-length binary-string column or parameter
and the length of the string is less than the length attribute of the target,
the string is padded on the right with the necessary number of hexadecimal
zeroes.</p>
<a name="reta"></a>
<h5 id="reta">Retrieval assignment</h5><a id="idx450" name="idx450"></a>
<p>The length of a string assigned to a variable can be greater than the length
attribute of the variable. When a string is assigned to a variable and the
string is longer than the length attribute of the variable, the string is
truncated on the right by the necessary number of bytes. When this occurs,
an SQLSTATE of '01004' is assigned to the RETURNED_SQLSTATE condition area
item in the SQL Diagnostics Area (or the value 'W' is assigned to
the SQLWARN1 field of the SQLCA).</p>
<p>When a string is assigned to a fixed-length binary-string variable and
the length of the string is less than the length attribute of the target,
the string is padded on the right with the necessary number of hexadecimal
zeroes.</p>
<p>When a string of length <span class="italic">n</span> is assigned to a varying-length
string variable with a maximum length greater than <span class="italic">n</span>,
the bytes after the <span class="italic">n</span>th byte of the variable are undefined.</p>
<a name="wq174"></a>
<h4 id="wq174">Character and graphic string assignments</h4><a id="idx451" name="idx451"></a><a id="idx452" name="idx452"></a><a id="idx453" name="idx453"></a><a id="idx454" name="idx454"></a>
<p>The following rules apply when the assignment target is a string. When
a datetime data type is involved, see <a href="rbafzmstch2bas.htm#dta">Datetime assignments</a>. For the special
considerations that apply when a distinct type is involved in an assignment,
especially to a variable, see <a href="rbafzmstch2bas.htm#udtasgn">Distinct type assignments</a>.</p>
<a name="wq175"></a>
<h5 id="wq175">Numeric to strings</h5>
<p>When a number is assigned to a string data type, it is converted to the
target string data type using the rules for a CAST specification. For more
information, see <a href="rbafzmstdatetimearith.htm#cast">CAST specification</a>.</p>
<a name="wq176"></a>
<h5 id="wq176">Storage assignment</h5>
<p>The basic rule is that the length of a string assigned to a column or parameter
of a function or procedure must not be greater than the length attribute of
the column or parameter. If the string is longer than the length attribute
of that column or parameter, an error is returned. Trailing blanks are normally
included in the length of the string. For storage assignments, however, trailing
blanks are not included in the length of the string.</p>
<p>When
a string is assigned to a fixed-length string column or parameter and the
length of the string is less than the length attribute of the target, the
string is padded on the right with the necessary number of single-byte, double-byte,
or UTF-16 or UCS-2 blanks.<sup class="fn"><a href="rbafzmstch2bas.htm#fn13">22</a></sup> The pad character is always
a blank, even for bit data.</p>
<a name="wq177"></a>
<h5 id="wq177">Retrieval assignment</h5><a id="idx455" name="idx455"></a>
<p>The length of a string assigned to a variable can be greater than the length
attribute of the variable. When a string is assigned to a variable and the
string is longer than the length attribute of the variable, the string is
truncated on the right by the necessary number of characters. When this occurs,
an SQLSTATE of '01004' is assigned to the RETURNED_SQLSTATE condition area
item in the SQL Diagnostics Area (or the value 'W' is assigned to
the SQLWARN1 field of the SQLCA). Furthermore, if an indicator variable is
provided, it is set to the original length of the string. If only the NUL-terminator
is truncated for a C NUL-terminated host variable and the *NOCNULRQD option
was specified on the CRTSQLCI or CRTSQLCPPI command (or CNULRQD(*NO) on the
SET OPTION statement), an SQLSTATE of '01004' is assigned to the RETURNED_SQLSTATE
condition area item in the SQL Diagnostics Area (or the value of 'N'
is assigned to the SQLWARN1 field of the SQLCA) and a NUL is not placed in
the variable.</p>
<p>When a string is assigned to a fixed-length variable and the length of
the string is less than the length attribute of the target, the string is
padded on the right with the necessary number of single-byte, double-byte,
or UTF-16 or UCS-2 blanks.<sup class="fn"><a href="rbafzmstch2bas.htm#fn13">22</a></sup> The pad character is always
a blank, even for bit data.</p>
<p>When a string of length <span class="italic">n</span> is assigned to a varying-length
string variable with a maximum length greater than <span class="italic">n</span>,
the characters after the <span class="italic">n</span>th character of the variable
are undefined.</p>
<a name="wq178"></a>
<h5 id="wq178">Assignments to mixed strings</h5><a id="idx456" name="idx456"></a><a id="idx457" name="idx457"></a><a id="idx458" name="idx458"></a>
<p>If a string contains mixed data, the assignment rules may require truncation
within a sequence of double-byte codes. To prevent the loss of the shift-in
character that ends the double-byte sequence, additional characters may be
truncated from the end of the string, and a shift-in character added. In the
truncated result, there is always an even number of bytes between each shift-out
character and its matching shift-in character.</p>
<a name="wq179"></a>
<h5 id="wq179">Assignments to C NUL-terminated strings</h5><a id="idx459" name="idx459"></a><a id="idx460" name="idx460"></a>
<p>When a string of length <span class="italic">n</span> is assigned to a C NUL-terminated
string variable with a length greater than <span class="italic">n+1</span>: </p>
<ul>
<li>If the *CNULRQD option was specified on the CRTSQLCI or CRTSQLCPPI command
(or CNULRQD(*YES) on the SET OPTION statement), the string is padded on the
right with x-n-1 blanks where x is the length of the variable. The padded
string is then assigned to the variable and the NUL-terminator is placed in
the next character position.</li>
<li>If the *NOCNULRQD precompiler option was specified on the CRTSQLCI or
CRTSQLCPPI command (or CNULRQD(*NO) on the SET OPTION statement), the string
is not padded on the right. The string is assigned to the variable and the
NUL-terminator is placed in the next character position.</li></ul>
<a name="craj"></a>
<h5 id="craj">Conversion rules for assignments</h5><a id="idx461" name="idx461"></a><a id="idx462" name="idx462"></a>
<p>A string assigned to a column or variable is first converted, if necessary,
to the coded character set of the target. Character conversion is necessary
only if all of the following are true: </p>
<ul>
<li>The CCSIDs are different.</li>
<li>Neither CCSID is 65535.</li>
<li>The string is neither null nor empty.</li>
<li>The CCSID Conversion Selection Table indicates that conversion is necessary.</li></ul>
<p>An error occurs if: </p>
<ul>
<li>The CCSID Conversion Selection Table is used but does not contain any
information about the pair of CCSIDs.</li>
<li>A character of the string cannot be converted, and the operation is assignment
to a column or assignment to a host variable without an indicator variable.
For example, a double-byte character (DBCS) cannot be converted to a column
or host variable with a single-byte character (SBCS) CCSID.</li></ul>
<p>A warning occurs if: </p>
<ul>
<li>A character of the string is converted to the substitution character.</li>
<li>A character of the string cannot be converted, and the operation is assignment
to a host variable with an indicator variable. For example, a DBCS character
cannot be converted to a host variable with an SBCS CCSID. In this case, the
string is not assigned to the host variable and the indicator variable is
set to -2.</li></ul><a id="idx463" name="idx463"></a><a id="idx464" name="idx464"></a><a id="idx465" name="idx465"></a><a id="idx466" name="idx466"></a>
<p></p>
<a name="dta"></a>
<h3 id="dta"><a href="rbafzmst02.htm#ToC_159">Datetime assignments</a></h3><a id="idx467" name="idx467"></a><a id="idx468" name="idx468"></a>
<p>A value assigned to a DATE column must be a date or a valid string representation
of a date. A date can only be assigned to a DATE column, a string column,
a string variable, or a date variable. A value assigned to a TIME column must
be a time or a valid string representation of a time. A time can only be assigned
to a TIME column, a string column, a string variable, or a time variable.
A value assigned to a TIMESTAMP column must be a timestamp or a valid string
representation of a timestamp. A timestamp can only be assigned to a TIMESTAMP
column, a string column, a string variable, or a timestamp variable.</p>
<p>When a datetime value is assigned to a string variable or column, it is
converted to its string representation. Leading zeros are not omitted from
any part of the date, time, or timestamp. The required length of the target
varies depending on the format of the string representation. If the length
of the target is greater than required, it is padded on the right with blanks.
If the length of the target is less than required, the result depends on the
type of datetime value involved and on the type of target. </p>
<ul>
<li>If the target is a string column, truncation is not allowed. The following
rules apply:
<p><span class="bold">DATE</span> </p>
<ul class="simple">
<li>The length attribute of the column must be at least 10 if the date format
is *ISO, USA, *EUR, or *JIS. If the date format is *YMD, *MDY, or *DMY, the
length attribute of the column must be at least 8. If the date format is *JUL,
the length of the variable must be at least 6.</li></ul>
<p><span class="bold">TIME</span> </p>
<ul class="simple">
<li>The length attribute of the column must be at least 8.</li></ul>
<p><span class="bold">TIMESTAMP</span> </p>
<ul class="simple">
<li>The length attribute of the column must be at least 26.</li></ul></li>
<li>When the target is a variable, the following rules apply:
<p><span class="bold">DATE</span> <a id="idx469" name="idx469"></a></p>
<ul class="simple">
<li>The length of the variable must be at least 10 if the date format is *ISO,
*USA, *EUR, or *JIS. If the date format is *YMD, *MDY, or *DMY, the length
of the variable must be at least 8. If the date format is *JUL, the length
of the variable must be at least 6.</li></ul>
<p><span class="bold">TIME</span> <a id="idx470" name="idx470"></a></p>
<ul>
<li>If the *USA format is used, the length of the variable must not be less
than 8. This format does not include seconds.</li>
<li>If the *ISO, *EUR, *JIS, or *HMS time format is used, the length of the
variable must not be less than 5. If the length is 5, 6, or 7, the seconds
part of the time is omitted from the result, and SQLWARN1 is set to 'W'.
In this case, the seconds part of the time is assigned to the indicator variable
if one is provided, and, if the length is 6 or 7, blank padding occurs so
that the value is a valid string representation of a time.</li></ul>
<p><span class="bold">TIMESTAMP</span> <a id="idx471" name="idx471"></a><a id="idx472" name="idx472"></a></p>
<ul class="simple">
<li>The length of the variable must not be less than 19. If the length is
between 19 and 25, the timestamp is truncated like a string, causing the omission
of one or more digits of the microsecond part. If the length is 20, the trailing
decimal point is replaced by a blank so that the value is a valid string representation
of a timestamp.</li></ul></li></ul>
<a name="wq180"></a>
<h3 id="wq180"><a href="rbafzmst02.htm#ToC_160">DataLink assignments</a></h3><a id="idx473" name="idx473"></a><a id="idx474" name="idx474"></a>
<p>The assignment of a value to a DataLink column results in the establishment
of a link to a file unless the linkage attributes of the value are empty or
the column is defined with NO LINK CONTROL. In cases where a linked value
already exists in the column, that file is unlinked. Assigning a null value
where a linked value already exists also unlinks the file associated with
the old value.</p>
<p>If the application provides the same data location as already exists in
the column, the link is retained. There are two reasons that this might be
done: </p>
<ul>
<li>the comment is being changed</li>
<li>if the table is placed in link pending state, the links in the table can
be reinstated by providing linkage attributes identical to the ones in the
column.</li></ul>
<p>A DataLink value may be assigned to a column by using the DLVALUE scalar
function. The DLVALUE scalar function creates a new DataLink value which can
then be assigned a column. Unless the value contains only a comment or the
URL is exactly the same, the act of assignment will link the file.</p>
<p>When assigning a value to a DataLink column, the following error conditions
can occur: </p>
<ul>
<li>Data Location (URL) format is invalid</li>
<li>File server is not registered with this database</li>
<li>Invalid link type specified</li>
<li>Invalid length of comment or URL
<p>Note that the size of a URL parameter
or function result is the same on both input or output and is bound by the
length of the DataLink column. However, in some cases the URL value returned
has an access token attached. In situations where this is possible, the output
location must have sufficient storage space for the access token and the length
of the DataLink column. Hence, the actual length of the comment and URL in
its fully expanded form provided on input should be restricted to accommodate
the output storage space. If the restricted length is exceeded, this error
is raised.</p></li></ul>
<p>When the assignment is also creating a link, the following errors can occur: </p>
<ul>
<li>File server not currently available.</li>
<li>File does not exist.</li>
<li>Referenced file cannot be accessed for linking.</li>
<li>File already linked to another column.
<p>Note that this error will be
raised even if the link is to a different relational database.</p></li></ul>
<p>In addition, when the assignment removes an existing link, the following
errors can occur: </p>
<ul>
<li>File server not currently available.</li>
<li>File with referential integrity control is not in a correct state according
to the DB2&reg; DataLinks File Manager.</li></ul>
<p>A DataLink value may be retrieved from the database through the use of
scalar functions (such as DLLINKTYPE and DLURLPATH). The results of these
scalar functions can then be assigned to variables.</p>
<p>Note that usually no attempt is made to access the file server at retrieval
time. <sup class="fn"><a id="wq181" name="wq181" href="rbafzmstch2bas.htm#wq182">23</a></sup>It is therefore possible that subsequent attempts to access the file
server through file system commands might fail.</p>
<p>A warning may be returned when retrieving a DataLink value because the
table is in link pending state.</p>
<a name="wq183"></a>
<h3 id="wq183"><a href="rbafzmst02.htm#ToC_161">Row ID assignments</a></h3><a id="idx475" name="idx475"></a><a id="idx476" name="idx476"></a>
<p>A row ID value can only be assigned to a column, parameter, or variable
with a row ID data type. For the value of the ROWID column, the column must
be defined as GENERATED BY DEFAULT or OVERRIDING SYSTEM VALUE must be specified.
A unique constraint is implicitly added to every table that has a ROWID column
that guarantees that every ROWID value is unique. The value that is specified
for the column must be a valid row ID value that was previously generated
by DB2 UDB for z/OS or DB2 UDB for iSeries.</p>
<a name="udtasgn"></a>
<h3 id="udtasgn"><a href="rbafzmst02.htm#ToC_162">Distinct type assignments</a></h3><a id="idx477" name="idx477"></a><a id="idx478" name="idx478"></a>
<p>The rules that apply to the assignments of distinct types to variables are different
than the rules for all other assignments that involve distinct types.</p>
<a name="wq184"></a>
<h4 id="wq184">Assignments to variables</h4>
<p>The assignment of a distinct type to a variable is based on the source
data type of the distinct type. Therefore, the value of a distinct type is
assignable to a variable only if the source data type of the distinct type
is assignable to the variable.</p>
<p><var class="pv">Example:</var> Assume that distinct type AGE was created with the following
SQL statement and column STU_AGE in table STUDENTS was defined with that distinct
type. Using the CL_SCHED table, select all the classes (CLASS_CODE) that start
(STARTING) later today. Today's classes have a value of 3 in the DAY column. </p>
<pre class="xmp"> <span class="bold">CREATE DISTINCT TYPE</span> AGE <span class="bold">AS SMALLINT WITH COMPARISONS</span></pre>
<p> When the statement is executed, the following cast functions are also
generated: </p>
<pre class="xmp"> AGE <span class="bold">(SMALLINT) RETURNS</span> AGE
AGE <span class="bold">(INTEGER) RETURNS</span> AGE
SMALLINT (AGE) <span class="bold">RETURNS SMALLINT</span></pre>
<p>Next, assume that column STU_AGE was defined in table STUDENTS with distinct
type AGE. Now, consider this valid assignment of a student's age to host
variable HV_AGE, which has an INTEGER data type: </p>
<pre class="xmp"> <span class="bold">SELECT </span> STU_AGE <span class="bold">INTO</span> :HV_AGE <span class="bold">FROM</span> STUDENTS <span class="bold">WHERE</span> STU_NUMBER = 200</pre>
<p>The distinct type value is assignable to the host variable HV_AGE because
the source data type of the distinct type (SMALLINT) is assignable to the
host variable (INTEGER). If distinct type AGE had been sourced on a character
data type such as CHAR(5), the above assignment would be invalid because a
character type cannot be assigned to an integer type.</p>
<a name="wq185"></a>
<h4 id="wq185">Assignments other than to variables</h4>
<p>A distinct type can be either the source or target of an assignment. Assignment
is based on whether the data type of the value to be assigned is castable
to the data type of the target. <a href="rbafzmstcastdt.htm#castdt">Casting between data types</a> shows which casts are
supported when a distinct type is involved. Therefore, a distinct type value
can be assigned to any target other than a variable when:</p>
<ul>
<li>The target of the assignment has the same distinct type, or</li>
<li>The distinct type is castable to the data type of the target</li></ul>
<p>Any value can be assigned to a distinct type when: </p>
<ul>
<li>The value to be assigned has the same distinct type as the target, or</li>
<li>The data type of the assigned value is castable to the target distinct
type</li></ul>
<p><var class="pv">Example:</var> Assume that the source data type for distinct type AGE
is SMALLINT: </p>
<pre class="xmp"> <span class="bold">CREATE DISTINCT TYPE</span> AGE <span class="bold">AS SMALLINT WITH COMPARISONS</span></pre>
<p>Next, assume that two tables TABLE1 and TABLE2 were created with four identical
column descriptions:</p>
<pre class="xmp"> AGECOL AGE
SMINTCOL SMALLINT
INTCOL INTEGER
DECCOL DEC(6,2) </pre>
<p>Using the following SQL statement and substituting various values for X
and Y to insert values into various columns of TABLE1 from TABLE2, <a href="rbafzmstch2bas.htm#assdtt1">Table 16</a> shows
whether the assignments are valid. </p>
<pre class="xmp"> <span class="bold">INSERT INTO </span> TABLE1 (Y) <span class="bold">SELECT</span> X <span class="bold">FROM</span> TABLE2</pre>
<a name="assdtt1"></a>
<table id="assdtt1" width="100%" summary="" border="1" frame="border" rules="rows">
<caption>Table 16. Assessment of various assignments (for example on INSERT)</caption>
<thead valign="bottom">
<tr>
<th id="wq186" width="19%" align="left" valign="bottom">TABLE2.X</th>
<th id="wq187" width="19%" align="left" valign="bottom">TABLE1.Y</th>
<th id="wq188" width="19%" align="left" valign="bottom">Valid</th>
<th id="wq189" width="42%" align="left" valign="bottom">Reason</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left" valign="top" headers="wq186">AGECOL</td>
<td align="left" valign="top" headers="wq187">AGECOL</td>
<td align="left" valign="top" headers="wq188">Yes</td>
<td align="left" valign="top" headers="wq189">Source and target are same distinct type</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq186">SMINTCOL</td>
<td align="left" valign="top" headers="wq187">AGECOL</td>
<td align="left" valign="top" headers="wq188">Yes</td>
<td align="left" valign="top" headers="wq189">SMALLINT can be cast to AGE (because AGE's
source type is SMALLINT)</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq186">INTCOL</td>
<td align="left" valign="top" headers="wq187">AGECOL</td>
<td align="left" valign="top" headers="wq188">Yes</td>
<td align="left" valign="top" headers="wq189">INTEGER can be cast to AGE (because AGE's
source type is SMALLINT)</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq186">DECCOL</td>
<td align="left" valign="top" headers="wq187">AGECOL</td>
<td align="left" valign="top" headers="wq188">No</td>
<td align="left" valign="top" headers="wq189">DECIMAL cannot be cast to AGE</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq186">AGECOL</td>
<td align="left" valign="top" headers="wq187">SMINTCOL</td>
<td align="left" valign="top" headers="wq188">Yes</td>
<td align="left" valign="top" headers="wq189">AGE can be cast to its source type SMALLINT</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq186">AGECOL</td>
<td align="left" valign="top" headers="wq187">INTCOL</td>
<td align="left" valign="top" headers="wq188">No</td>
<td align="left" valign="top" headers="wq189">AGE cannot be cast to INTEGER</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq186">AGECOL</td>
<td align="left" valign="top" headers="wq187">DECCOL</td>
<td align="left" valign="top" headers="wq188">No</td>
<td align="left" valign="top" headers="wq189">AGE cannot be cast to DECIMAL</td>
</tr>
</tbody>
</table>
<a name="wq190"></a>
<h3 id="wq190"><a href="rbafzmst02.htm#ToC_165">Assignments to LOB locators</a></h3><a id="idx479" name="idx479"></a><a id="idx480" name="idx480"></a>
<p>When a LOB locator is used, it can refer to any string data. If a LOB locator
is used for the first fetch of a cursor and the cursor is on a remote server,
LOB locators must be used for all subsequent fetches unless the *NOOPTLOB
precompile option is used.</p>
<a name="wq191"></a>
<h3 id="wq191"><a href="rbafzmst02.htm#ToC_166">Numeric comparisons</a></h3><a id="idx481" name="idx481"></a><a id="idx482" name="idx482"></a><a id="idx483" name="idx483"></a><a id="idx484" name="idx484"></a>
<p>Numbers are compared algebraically; that is, with regard to sign. For example,
&ndash;2 is less than +1.</p>
<p>If one number is an integer and the other number is decimal, the comparison
is made with a temporary copy of the integer that has been converted to decimal.</p>
<p>When decimal or nonzero scale binary numbers with different scales are
compared, the comparison is made with a temporary copy of one of the numbers
that has been extended with trailing zeros so that its fractional part has
the same number of digits as the other number.</p>
<p>If one number is floating point and the other is integer, decimal, or single-precision
floating point, the comparison is made with a temporary copy of the second
number converted to a double-precision floating-point number. However, if
a single-precision floating-point column is compared to a constant and the
constant can be represented by a single-precision floating-point number, the
comparison is made with a single-precision form of the constant.</p>
<p>Two floating-point numbers are equal only if the bit configurations of
their normalized forms are identical.</p>
<p>When string and numeric data types are compared, the string is converted
to the numeric data type and must contain a valid string representation of
a number.</p>
<a name="wq192"></a>
<h3 id="wq192"><a href="rbafzmst02.htm#ToC_167">String comparisons</a></h3><a id="idx485" name="idx485"></a><a id="idx486" name="idx486"></a>
<a name="wq193"></a>
<h4 id="wq193">Binary string comparisons</h4>
<p>Binary string comparisons always use a sort sequence of *HEX and the corresponding
bytes of each string are compared. Additionally, two binary strings are equal
only if the lengths of the two strings are identical. If the strings are equal
up to the length of the shorter string length, the shorter string is considered
less than the longer string even when the remaining bytes in the longer string
are hexadecimal zeros. Note that binary strings cannot be compared to character
strings unless the character string is cast to a binary string.</p>
<a name="wq194"></a>
<h4 id="wq194">Character and graphic string comparisons</h4>
<p>Character and UTF-16 or UCS-2 graphic string comparisons use the sort sequence
in effect when the statement is executed for all SBCS data and the single-byte
portion of mixed data. If the sort sequence is *HEX, the corresponding bytes
of each string are compared. For all other sort sequences, the corresponding
bytes of the weighted value of each string are compared.</p>
<p>If the strings have different lengths, a temporary copy of the shorter
string is padded on the right with blanks before comparison. The padding makes
each string the same length. The pad character is always a blank, regardless
of the sort sequence. For bit data, the pad character is also a blank. For
DBCS graphic data, the pad character is a DBCS blank (x'4040'). For UTF-16
or UCS-2 graphic data, the pad character is a UTF-16 blank. <sup class="fn"><a id="wq195" name="wq195" href="rbafzmstch2bas.htm#wq196">24</a></sup></p>
<p>Two strings are equal if any of the following are true: </p>
<ul>
<li>Both strings are empty.</li>
<li>A *HEX sort sequence is used and all corresponding bytes are equal.</li>
<li>A sort sequence other than *HEX is used and all corresponding bytes of
the weighted value are equal.</li></ul><p class="indatacontent"> An empty string is equal to a blank string. The relationship between
two unequal strings is determined by a comparison of the first pair of unequal
bytes (or bytes of the weighted value) from the left end of the string. This
comparison is made according to the sort sequence in effect when the statement
is executed.</p>
<p>In an application that will run in multiple environments, the same sort
sequence (which depends on the CCSIDs of the environments) must be used to
ensure identical results. The following table illustrates the differences
between EBCDIC, ASCII, and the DB2 UDB LUW default sort sequence for United States
English by showing a list that is sorted according to each one.</p>
<a name="csdtabl"></a>
<table id="csdtabl" width="100%" summary="" border="0" frame="void" rules="none">
<caption>Table 17. Sort Sequence Differences</caption>
<thead valign="bottom">
<tr>
<th id="wq197" width="33%" align="left">ASCII and Unicode</th>
<th id="wq198" width="33%" align="left">EBCDIC</th>
<th id="wq199" width="33%" align="left">DB2 UDB LUW Default</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td headers="wq197"><tt class="xph">0000</tt></td>
<td headers="wq198"><tt class="xph">@@@@</tt></td>
<td headers="wq199"><tt class="xph">0000</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">9999</tt></td>
<td headers="wq198"><tt class="xph">co-op</tt></td>
<td headers="wq199"><tt class="xph">9999</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">@@@@</tt></td>
<td headers="wq198"><tt class="xph">coop</tt></td>
<td headers="wq199"><tt class="xph">@@@@</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">COOP</tt></td>
<td headers="wq198"><tt class="xph">piano forte</tt></td>
<td headers="wq199"><tt class="xph">co-op</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">PIANO-FORTE</tt></td>
<td headers="wq198"><tt class="xph">piano-forte</tt></td>
<td headers="wq199"><tt class="xph">COOP</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">co-op</tt></td>
<td headers="wq198"><tt class="xph">COOP</tt></td>
<td headers="wq199"><tt class="xph">coop</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">coop</tt></td>
<td headers="wq198"><tt class="xph">PIANO-FORTE</tt></td>
<td headers="wq199"><tt class="xph">piano forte</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">piano forte</tt></td>
<td headers="wq198"><tt class="xph">0000</tt></td>
<td headers="wq199"><tt class="xph">PIANO-FORTE</tt></td>
</tr>
<tr>
<td headers="wq197"><tt class="xph">piano-forte</tt></td>
<td headers="wq198"><tt class="xph">9999</tt></td>
<td headers="wq199"><tt class="xph">piano-forte</tt></td>
</tr>
</tbody>
</table>
<p>Two varying-length strings with different lengths are equal if they differ
only in the number of trailing blanks. In operations that select one value
from a set of such values, the value selected is arbitrary. The operations
that can involve such an arbitrary selection are DISTINCT, MAX, MIN, UNION,
EXCEPT, INTERSECT, and references to a grouping column. See the description
of GROUP BY for further information about the arbitrary selection involved
in references to a grouping column.</p>
<a name="crcj"></a>
<h5 id="crcj">Conversion rules for comparison</h5><a id="idx487" name="idx487"></a>
<p>When two strings are compared, one of the strings is first converted, if
necessary, to the coded character set of the other string. Character conversion
is necessary only if all of the following are true: </p>
<ul>
<li>The CCSIDs of the two strings are different.</li>
<li>Neither CCSID is 65535.</li>
<li>The string selected for conversion is neither null nor empty.</li>
<li>The CCSID Conversion Selection Table (<a href="rbafzmstccseta.htm#conccsid">Coded character sets and CCSIDs</a>) indicates
that conversion is necessary.</li></ul>
<p>If two strings with different encoding schemes are compared,
any necessary conversion applies to the string as follows:</p>
<a name="wq200"></a>
<table id="wq200" width="100%" summary="" border="1" frame="border" rules="all">
<caption>Table 18. Selecting the Encoding Scheme for Character Conversion</caption>
<thead valign="bottom">
<tr>
<th id="wq201" width="33%" rowspan="2" align="left" valign="bottom">First Operand</th>
<th id="wq202" colspan="4" align="center" valign="bottom">Second
Operand</th>
</tr>
<tr>
<th id="wq203" width="16%" align="left" valign="bottom">SBCS Data</th>
<th id="wq204" width="16%" align="left" valign="bottom">DBCS Data</th>
<th id="wq205" width="16%" align="left" valign="bottom">Mixed Data</th>
<th id="wq206" width="16%" align="left" valign="bottom">UTF-16 or UCS-2 Data</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center" valign="top" headers="wq201">SBCS Data</td>
<td align="center" valign="top" headers="wq202 wq203">see below</td>
<td align="center" valign="top" headers="wq202 wq204">second</td>
<td align="center" valign="top" headers="wq202 wq205">second</td>
<td align="center" valign="top" headers="wq202 wq206">second</td>
</tr>
<tr>
<td align="center" valign="top" headers="wq201">DBCS Data</td>
<td align="center" valign="top" headers="wq202 wq203">first</td>
<td align="center" valign="top" headers="wq202 wq204">see below</td>
<td align="center" valign="top" headers="wq202 wq205">second</td>
<td align="center" valign="top" headers="wq202 wq206">second</td>
</tr>
<tr>
<td align="center" valign="top" headers="wq201">Mixed Data</td>
<td align="center" valign="top" headers="wq202 wq203">first</td>
<td align="center" valign="top" headers="wq202 wq204">first</td>
<td align="center" valign="top" headers="wq202 wq205">see below</td>
<td align="center" valign="top" headers="wq202 wq206">second</td>
</tr>
<tr>
<td align="center" valign="top" headers="wq201">UTF-16 or UCS-2 Data</td>
<td align="center" valign="top" headers="wq202 wq203">first</td>
<td align="center" valign="top" headers="wq202 wq204">first</td>
<td align="center" valign="top" headers="wq202 wq205">first</td>
<td align="center" valign="top" headers="wq202 wq206">see below</td>
</tr>
</tbody>
</table>
<p>Otherwise, the string selected for conversion depends on the type of each
operand. The following table shows which operand is selected for conversion,
given the operand types:</p>
<a name="wq207"></a>
<table id="wq207" width="100%" summary="" border="1" frame="border" rules="all">
<caption>Table 19. Selecting the Operand for Character Conversion</caption>
<thead valign="bottom">
<tr>
<th id="wq208" width="28%" rowspan="2" align="left" valign="bottom">First Operand</th>
<th id="wq209" colspan="5" align="center" valign="bottom">Second
Operand</th>
</tr>
<tr>
<th id="wq210" width="14%" align="left" valign="bottom">Column Value</th>
<th id="wq211" width="14%" align="left" valign="bottom">Derived Value</th>
<th id="wq212" width="14%" align="left" valign="bottom">Special Register</th>
<th id="wq213" width="14%" align="left" valign="bottom">Constant</th>
<th id="wq214" width="14%" align="left" valign="bottom">Variable</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left" valign="top" headers="wq208">Column Value</td>
<td align="left" valign="top" headers="wq209 wq210">second</td>
<td align="left" valign="top" headers="wq209 wq211">second</td>
<td align="left" valign="top" headers="wq209 wq212">second</td>
<td align="left" valign="top" headers="wq209 wq213">second</td>
<td align="left" valign="top" headers="wq209 wq214">second</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq208">Derived Value</td>
<td align="left" valign="top" headers="wq209 wq210">first</td>
<td align="left" valign="top" headers="wq209 wq211">second</td>
<td align="left" valign="top" headers="wq209 wq212">second</td>
<td align="left" valign="top" headers="wq209 wq213">second</td>
<td align="left" valign="top" headers="wq209 wq214">second</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq208">Special Register</td>
<td align="left" valign="top" headers="wq209 wq210">first</td>
<td align="left" valign="top" headers="wq209 wq211">first</td>
<td align="left" valign="top" headers="wq209 wq212">second</td>
<td align="left" valign="top" headers="wq209 wq213">second</td>
<td align="left" valign="top" headers="wq209 wq214">second</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq208">Constant</td>
<td align="left" valign="top" headers="wq209 wq210">first</td>
<td align="left" valign="top" headers="wq209 wq211">first</td>
<td align="left" valign="top" headers="wq209 wq212">first</td>
<td align="left" valign="top" headers="wq209 wq213">second</td>
<td align="left" valign="top" headers="wq209 wq214">second</td>
</tr>
<tr>
<td align="left" valign="top" headers="wq208">Variable</td>
<td align="left" valign="top" headers="wq209 wq210">first</td>
<td align="left" valign="top" headers="wq209 wq211">first</td>
<td align="left" valign="top" headers="wq209 wq212">first</td>
<td align="left" valign="top" headers="wq209 wq213">first</td>
<td align="left" valign="top" headers="wq209 wq214">second</td>
</tr>
</tbody>
</table>
<p>A variable that contains data in a foreign encoding scheme is always effectively
converted to the native encoding scheme before it is used in any operation.
The above rules are based on the assumption that this conversion has already
occurred.</p>
<p>An error is returned if a character of the string cannot be converted or
the CCSID Conversion Selection Table (<a href="rbafzmstccseta.htm#conccsid">Coded character sets and CCSIDs</a>) is used but
does not contain any information about the pair of CCSIDs. A warning occurs
if a character of the string is converted to the substitution character.</p>
<a name="wq215"></a>
<h3 id="wq215"><a href="rbafzmst02.htm#ToC_171">Datetime comparisons</a></h3><a id="idx488" name="idx488"></a><a id="idx489" name="idx489"></a>
<p>A DATE, TIME, or TIMESTAMP value can be compared either with another value
of the same data type or with a string representation of that data type. All
comparisons are chronological, which means the farther a point in time is
from January 1, 0001, the <span class="italic">greater</span> the value of that
point in time.</p>
<p>Comparisons involving TIME values and string representations of time values
always include seconds. If the string representation omits seconds, zero seconds
are implied. The time 24:00:00 compares greater than the time 00:00:00.</p>
<p>Comparisons involving TIMESTAMP values are chronological without regard
to representations that might be considered equivalent. Thus, the following
predicate is true: </p>
<a name="r3tmstp"></a>
<pre id="r3tmstp" class="xmp"> <span class="bold">TIMESTAMP</span>('1990-02-23-00.00.00') > '1990-02-22-24.00.00'</pre>
<a name="wq216"></a>
<h3 id="wq216"><a href="rbafzmst02.htm#ToC_172">DataLink comparisons</a></h3><a id="idx490" name="idx490"></a><a id="idx491" name="idx491"></a>
<p>A DATALINK operand cannot be directly compared to any data type. The DLCOMMENT,
DLLINKTYPE, DLURLCOMPLETE, DLURLPATH, DLURLPATHONLY, DLURLSCHEME, and DLURLSERVER
scalar functions can be used to extract character string values from a datalink
which can then be compared to other strings.</p>
<a name="wq217"></a>
<h3 id="wq217"><a href="rbafzmst02.htm#ToC_173">Row ID comparisons</a></h3><a id="idx492" name="idx492"></a><a id="idx493" name="idx493"></a>
<p>A ROWID operand cannot be directly compared to any data type. To compare
the bit representation of a ROWID, first cast the ROWID to a character string.</p>
<a name="wq218"></a>
<h3 id="wq218"><a href="rbafzmst02.htm#ToC_174">Distinct type comparisons</a></h3><a id="idx494" name="idx494"></a><a id="idx495" name="idx495"></a>
<p>A value with a distinct type can be compared only to another value with
exactly the same distinct type.</p>
<p>For example, assume that distinct type YOUTH and table CAMP_DB2_ROSTER
table were created with the following SQL statements: </p>
<pre class="xmp"> <span class="bold">CREATE DISTINCT TYPE</span> YOUTH <span class="bold">AS INTEGER WITH COMPARISONS</span>
<span class="bold">CREATE TABLE</span> CAMP_DB2_ROSTER
<span class="bold">(</span> NAME <span class="bold">VARCHAR(</span>20<span class="bold">),</span>
ATTENDEE_NUMBER <span class="bold">INTEGER NOT NULL,</span>
AGE YOUTH<span class="bold">,</span>
HIGH_SCHOOL_LEVEL YOUTH<span class="bold">)</span></pre>
<p>The following comparison is valid because AGE and HIGH_SCHOOL_LEVEL have
the same distinct type:</p>
<pre class="xmp"> <span class="bold">SELECT * FROM</span> CAMP_DB2_ROSTER
<span class="bold">WHERE</span> AGE <span class="bold">></span> HIGH_SCHOOL_LEVEL </pre>
<p>The following comparison is not valid:</p>
<pre class="xmp"> <span class="bold">SELECT * FROM</span> CAMP_DB2_ROSTER ***INCORRECT***
<span class="bold">WHERE</span> AGE <span class="bold">></span> ATTENDEE_NUMBER</pre>
<p>However, AGE can be compared to ATTENDEE_NUMBER by using a cast function
or CAST specification to cast between the distinct type and the source type.
All of the following comparisons are valid: </p>
<pre class="xmp"> <span class="bold">SELECT * FROM</span> CAMP_DB2_ROSTER
<span class="bold">WHERE</span> AGE <span class="bold">></span> YOUTH<span class="bold">(</span>ATTENDEE_NUMBER<span class="bold">)</span>
<span class="bold">SELECT * FROM</span> CAMP_DB2_ROSTER
<span class="bold">WHERE</span> AGE <span class="bold">> CAST(</span> ATTENDEE_NUMBER <span class="bold">AS</span> YOUTH<span class="bold">)</span>
<span class="bold">SELECT * FROM</span> CAMP_DB2_ROSTER
<span class="bold">WHERE INTEGER(</span>AGE<span class="bold">) ></span> ATTENDEE_NUMBER
<span class="bold">SELECT * FROM</span> CAMP_DB2_ROSTER
<span class="bold">WHERE CAST(</span>AGE <span class="bold">AS INTEGER) ></span> ATTENDEE_NUMBER
</pre><a id="idx496" name="idx496"></a>
<hr /><div class="fnnum"><a id="fn13" name="fn13">22</a>.</div>
<div class="fntext">UTF-16 or UCS-2 defines a blank character at code point X'0020'
and X'3000'. The database manager pads with the blank at code point X'0020'.
The database manager pads UTF-8 with a blank at code point X'20'</div><div class="fnnum"><a id="wq182" name="wq182" href="rbafzmstch2bas.htm#wq181">23</a>.</div>
<div class="fntext">It may be necessary to access the file server to determine the prefix
name associated with a path. This can be changed at the file server when the
mount point of a file system is moved. First access of a file on a server
will cause the required values to be retrieved from the file server and cached
at the database server for the subsequent retrieval of DataLink values for
that file server. An error is returned if the file server cannot be accessed.</div><div class="fnnum"><a id="wq196" name="wq196" href="rbafzmstch2bas.htm#wq195">24</a>.</div>
<div class="fntext">UTF-16 defines
a blank character at code point X'0020' and X'3000'. The database manager
pads with the blank at code point X'0020'.</div>
<br />
<hr /><br />
[ <a href="#Top_Of_Page">Top of Page</a> | <a href="rbafzmstcastdt.htm">Previous Page</a> | <a href="rbafzmstopcomb.htm">Next Page</a> | <a href="rbafzmst02.htm#wq1">Contents</a> |
<a href="rbafzmstindex.htm#index">Index</a> ]
<a id="Bot_Of_Page" name="Bot_Of_Page"></a>
</body>
</html>
Reference in New Issue Copy Permalink