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<a name="ch2pred"></a>
<h2 id="ch2pred"><a href="rbafzmst02.htm#ToC_288">Predicates</a></h2><a id="idx752" name="idx752"></a>
<p>A <span class="italic">predicate</span> specifies a condition that is true,
false, or unknown about a given row or group.</p>
<p>The following rules apply to all types of predicates: </p>
<ul>
<li>Predicates are evaluated after the expressions that are operands of the
predicate.</li>
<li>All values specified in the same predicate must be compatible.</li>
<li>The value of a variable may be null (that is, the variable may have a
negative indicator variable).</li>
<li>The CCSID conversion of operands of predicates involving two or more operands
are done according to <a href="rbafzmstch2bas.htm#crcj">Conversion rules for comparison</a>.</li>
<li>Use of a DataLink value is limited to the NULL predicate.</li></ul>
<p><span class="bold">Row-value expression</span>: The operand of several
predicates (basic, quantified, and IN) can be a <span class="italic">row-value-expression</span>:<a id="idx753" name="idx753"></a>
<a href="rbafzmstch2pred.htm#synrve"><img src="c.gif" alt="Click to skip syntax diagram" /></a></p>
<a name="wq387"></a>
<div class="fignone" id="wq387">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn28.htm"
border="0" /></span><a href="#skipsyn-27"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a> .-,----------.
V |
>>-(----<span class="italic">expression</span>-+--)---------------------------------------->&lt;
</pre>
<a name="skipsyn-27" id="skipsyn-27"></a></div>
<a name="synrve"></a>
<p id="synrve">A <span class="italic">row-value-expression</span> returns
a single row that consists of one or more column values. The values can be
specified as a list of expressions. The number of columns that are returned
by the <span class="italic">row-value-expression</span> is equal to the number
of expressions that are specified in the list.</p>
<a name="baspred"></a>
<h3 id="baspred"><a href="rbafzmst02.htm#ToC_289">Basic predicate</a></h3><a id="idx754" name="idx754"></a><a id="idx755" name="idx755"></a>
<a href="rbafzmstch2pred.htm#synbasic"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq388"></a>
<div class="fignone" id="wq388">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn29.htm"
border="0" /></span><a href="#skipsyn-28"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a> (1)
>>-+-<span><span class="italic">expression</span></span>--+-<span>&nbsp;=&nbsp;</span>--+-------<span><span class="italic">expression</span></span>----------------------------+->&lt;
| +-<span>&nbsp;&lt;>&nbsp;</span>-+ |
| +-<span>&nbsp;&lt;&nbsp;</span>--+ |
| +-<span>&nbsp;>&nbsp;</span>--+ |
| +-<span>&nbsp;&lt;=&nbsp;</span>-+ |
| '-<span>&nbsp;>=&nbsp;</span>-' |
+-<span>(</span>--<span><span class="italic">row-value-expression</span></span>--<span>)</span>--+-<span>&nbsp;=&nbsp;</span>--+--<span>(</span>--<span><span class="italic">row-value-expression</span></span>--<span>)</span>-+
| '-<span>&nbsp;&lt;>&nbsp;</span>-' |
+-<span><span>(</span>--<span><span><span class="italic">fullselect</span></span>--<span><span>)</span>--+-<span><span>&nbsp;=&nbsp;</span>--+--<span><span>(</span>--<span><span><span class="italic">row-value-expression</span></span>--<span><span>)</span>-----------+
| '-<span><span>&nbsp;&lt;>&nbsp;</span>-' |
'-<span><span>(</span>--<span><span><span class="italic">row-value-expression</span></span>--<span><span>)</span>--+-<span><span>&nbsp;=&nbsp;</span>--+--<span><span>(</span>--<span><span><span class="italic">fullselect</span></span>--<span><span>)</span>-----------'
'-<span><span>&nbsp;&lt;>&nbsp;</span>-'
</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></pre>
<a name="skipsyn-28" id="skipsyn-28"></a>
<a name="wq389"></a>
<div class="notelisttitle" id="wq389">Notes:</div>
<ol type="1">
<li>Other comparison operators are also supported. </li>
</ol></div>
<p>A <span class="italic">basic predicate</span> compares two values
or compares a set of values with another set of values.</p>
<p>When a single <span class="italic">expression</span> is specified
on the left side of the operator, another <span class="italic">expression</span> must
be specified on the right side. The data types of the corresponding expressions
must be compatible. The value of the expression on the left side is compared
with the value of the expression on the right side. If the value of either
operand is null, the result of the predicate is unknown. Otherwise the result
is either true or false.</p>
<p>When a <span class="italic">row-value-expression</span> is specified
on the left side of the operator (= or &lt;>) and another <span class="italic">row-value-expression</span> is specified on the right side of the operator,
both <span class="italic">row-value-expressions</span> must have the same number
of value expressions. The data types of the corresponding expressions of the <span class="italic">row-value-expressions</span> must be compatible. The value of
each expression on the left side is compared with the value of its corresponding
expression on the right side.</p>
<p>When a <span class="italic">row-value-expression</span> is specified
and a <span class="italic">fullselect</span> is also specified:</p>
<ul>
<li>SELECT * is not allowed in the outermost select lists of the <span class="italic">fullselect</span>.</li>
<li>The result table of the <span class="italic">fullselect</span> must have the
same number of columns as the <span class="italic">row-value-expression</span>.
The data types of the corresponding expressions of the <span class="italic">row-value-expression</span> and the <span class="italic">fullselect</span> must
be compatible. The value of each expression on the left side is compared with
the value of its corresponding expression on the right side.</li></ul>
<p>The result of the predicate depends on the operator:</p>
<ul>
<li>If the operator is =, the result of the predicate is:
<ul>
<li>True if all pairs of corresponding value expressions evaluate to true.</li>
<li>False if any one pair of corresponding value expressions evaluates to
false.</li>
<li>Otherwise, unknown (that is, if at least one comparison of corresponding
value expressions is unknown because of a null value and no pair of corresponding
value expressions evaluates to false).</li></ul></li>
<li>If the operator is &lt;>, the result of the predicate is:
<ul>
<li>True if any one pair of corresponding value expressions evaluates to true.</li>
<li>False if all pairs of corresponding value expressions evaluate to false.</li>
<li>Otherwise, unknown (that is, if at least one comparison of corresponding
value expressions is unknown because of a null value and no pair of corresponding
value expressions evaluates to true).</li></ul></li></ul>
<p>If the corresponding operands of the predicate are SBCS data, mixed data,
or Unicode data, and if the sort sequence in effect at the time the statement
is executed is not *HEX, then the comparison of the operands is performed
using weighted values for the operands. The weighted values are based on the
sort sequence.</p>
<p>For values <var class="pv">x</var> and <var class="pv">y</var>: </p>
<dl>
<dt class="bold">Predicate</dt>
<dd class="bold">Is true if and only if...</dd>
<dt class="bold"><tt class="xph"><var class="pv">x</var> = <var class="pv">y</var></tt></dt>
<dd><var class="pv">x</var> is equal to <var class="pv">y</var>
</dd>
<dt class="bold"><tt class="xph"><var class="pv">x</var>&lt;> <var class="pv">y</var></tt></dt>
<dd><var class="pv">x</var> is not equal to <var class="pv">y</var>
</dd>
<dt class="bold"><tt class="xph"><var class="pv">x</var> &lt; <var class="pv">y</var></tt></dt>
<dd><var class="pv">x</var> is less than <var class="pv">y</var>
</dd>
<dt class="bold"><tt class="xph"><var class="pv">x</var> > <var class="pv">y</var></tt></dt>
<dd><var class="pv">x</var> is greater than <var class="pv">y</var>
</dd>
<dt class="bold"><tt class="xph"><var class="pv">x</var>>= <var class="pv">y</var></tt></dt>
<dd><var class="pv">x</var> is greater than or equal to <var class="pv">y</var>
</dd>
<dt class="bold"><tt class="xph"><var class="pv">x</var>&lt;= <var class="pv">y</var></tt></dt>
<dd><var class="pv">x</var> is less than or equal to <var class="pv">y</var>
</dd>
</dl>
<a name="wq391"></a>
<h4 id="wq391">Examples</h4>
<p><span class="italic">Example 1</span></p>
<pre class="xmp"> EMPNO = '528671'
PRTSTAFF &lt;> :VAR1
SALARY + BONUS + COMM &lt; 20000
SALARY > <span class="bold">(SELECT AVG(</span>SALARY<span class="bold">)
FROM</span> EMPLOYEE<span class="bold">)</span></pre>
<p><span class="italic">Example 2</span>: List the name, first name,
and salary of the employee who is responsible for the 'OP1000' project.</p>
<pre class="xmp"> <span class="bold">SELECT</span> LASTNAME, FIRSTNME, SALARY
<span class="bold">FROM</span> EMPLOYEE X
<span class="bold">WHERE</span> EMPNO = <span class="bold">( SELECT </span> RESPEMP
<span class="bold">FROM</span> PROJA1 Y
<span class="bold">WHERE</span> MAJPROJ = 'OP1000' <span class="bold">)</span></pre>
<a name="wq392"></a>
<h3 id="wq392"><a href="rbafzmst02.htm#ToC_291">Quantified predicate</a></h3><a id="idx756" name="idx756"></a><a id="idx757" name="idx757"></a><a id="idx758" name="idx758"></a><a id="idx759" name="idx759"></a><a id="idx760" name="idx760"></a>
<a href="rbafzmstch2pred.htm#synqualified"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq393"></a>
<div class="fignone" id="wq393">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn30.htm"
border="0" /></span><a href="#skipsyn-29"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a> (1)
>>-+-<span class="italic">expression</span>--+-&nbsp;=&nbsp;--+-------+-SOME-+--(--<span class="italic">fullselect</span>--)-------+->&lt;
| +-&nbsp;&lt;>&nbsp;-+ +-ANY--+ |
| +-&nbsp;&lt;&nbsp;--+ '-ALL--' |
| +-&nbsp;>&nbsp;--+ |
| +-&nbsp;&lt;=&nbsp;-+ |
| '-&nbsp;>=&nbsp;-' |
+-(--<span class="italic">row-value-expression</span>--)--&nbsp;=&nbsp;--+-SOME-+--(--<span class="italic">fullselect</span>--)-+
| '-ANY--' |
'-(--<span class="italic">row-value-expression</span>--)--&nbsp;&lt;>&nbsp;--ALL--(--<span class="italic">fullselect</span>--)-----'
</pre>
<a name="skipsyn-29" id="skipsyn-29"></a>
<a name="wq394"></a>
<div class="notelisttitle" id="wq394">Notes:</div>
<ol type="1">
<li>Other comparison operators are also supported. </li>
</ol></div>
<a name="synqualified"></a>
<p id="synqualified">A <span class="italic">quantified predicate</span> compares a value or values with a set of values.</p>
<p>When <span class="italic">expression</span> is specified, the fullselect
must return a single result column. The fullselect can return any number of
values, whether null or not null. The result depends on the operator that
is specified:</p>
<ul>
<li>When ALL is specified, the result of the predicate is:
<ul>
<li>True if the result of the fullselect is empty, or if the specified
relationship is true for every value returned by the fullselect.</li>
<li>False if the specified relationship is false for at least one
value returned by the fullselect.</li>
<li>Unknown if the specified relationship is not false for any
values returned by the fullselect and at least one comparison is unknown because
of a null value.</li></ul></li>
<li>When SOME or ANY is specified, the result of the predicate is:
<ul>
<li>True if the specified relationship is true for at least one
value returned by the fullselect.</li>
<li>False if the result of the fullselect is empty, or if the specified
relationship is false for every value returned by the fullselect.</li>
<li>Unknown if the specified relationship is not true for any of
the values returned by the fullselect and at least one comparison is unknown
because of a null value.</li></ul></li></ul>
<p>When <span class="italic">row-value-expression</span> is specified,
the number of result columns returned by the fullselect must be the same as
the number of value expressions specified by <span class="italic">row-value-expression</span>. The fullselect can return any number of rows of values. The data types
of the corresponding expressions of the row value expressions must be compatible.
The value of each expression from <span class="italic">row-value-expression</span> is compared with the value of the corresponding result column from the
fullselect. SELECT * is not allowed in the outermost select lists of the <span class="italic">fullselect</span>.</p>
<p>The value of the predicate depends on the operator that is specified:</p>
<ul>
<li>When ALL is specified, the result of the predicate is:
<ul>
<li>True if the result of the fullselect is empty or if the specified
relationship is true for every row returned by fullselect.</li>
<li>False if the specified relationship is false for at least one
row returned by the fullselect.</li>
<li>Unknown if the specified relationship is not false for any
row returned by the fullselect and at least one comparison is unknown because
of a null value.</li></ul></li>
<li>When SOME or ANY is specified, the result of the predicate is:
<ul>
<li>True if the specified relationship is true for at least one
row returned by the fullselect.</li>
<li>False if the result of the fullselect is empty or if the specified
relationship is false for every row returned by the fullselect.</li>
<li>Unknown if the specified relationship is not true for any of
the rows returned by the fullselect and at least one comparison is unknown
because of a null value.</li></ul></li></ul>
<p>If the corresponding operands of the predicate are SBCS data, mixed data,
or Unicode data, and if the sort sequence in effect at the time the statement
is executed is not *HEX, then the comparison of the operands is performed
using weighted values for the operands. The weighted values are based on the
sort sequence.</p>
<a name="wq396"></a>
<h4 id="wq396">Examples</h4>
<p>&nbsp;</p>
<p>Table <span class="bold">TBLA</span> </p>
<pre class="xmp">COLA
-----
1
2
3
4
null</pre><p class="indatacontent"> Table <span class="bold">TBLB</span> </p>
<pre class="xmp">COLB
-----
2
3</pre>
<p><span class="italic">Example 1</span> </p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> TBLA <span class="bold">WHERE</span> COLA = <span class="bold">ANY(SELECT</span> COLB <span class="bold">FROM</span> TBLB<span class="bold">)</span></pre>
<p>Results in 2,3. The subselect returns (2,3). COLA in rows 2 and 3 equals
at least one of these values.</p>
<p><span class="italic">Example 2</span> </p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> TBLA <span class="bold">WHERE</span> COLA > <span class="bold">ANY(SELECT</span> COLB <span class="bold">FROM</span> TBLB<span class="bold">)</span></pre>
<p>Results in 3,4. The subselect returns (2,3). COLA in rows 3 and 4 is greater
than at least one of these values.</p>
<p><span class="italic">Example 3</span> </p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> TBLA <span class="bold">WHERE</span> COLA > <span class="bold">ALL(SELECT</span> COLB <span class="bold">FROM</span> TBLB<span class="bold">)</span></pre>
<p>Results in 4. The subselect returns (2,3). COLA in row 4 is the only one
that is greater than both these values.</p>
<p><span class="italic">Example 4</span> </p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> TBLA <span class="bold">WHERE</span> COLA > <span class="bold">ALL(SELECT</span> COLB <span class="bold">FROM</span> TBLB<span class="bold"> WHERE</span> COLB&lt;0<span class="bold">)</span></pre>
<p>Results in 1,2,3,4, and null. The subselect returns no values. Thus, the
predicate is true for all rows in TBLA.</p>
<p><span class="italic">Example 5</span> </p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> TBLA <span class="bold">WHERE</span> COLA > <span class="bold">ANY(SELECT</span> COLB <span class="bold">FROM</span> TBLB<span class="bold"> WHERE</span> COLB&lt;0<span class="bold">)</span></pre>
<p>Results in the empty set. The subselect returns no values. Thus, the predicate
is false for all rows in TBLA.</p>
<a name="wq397"></a>
<h3 id="wq397"><a href="rbafzmst02.htm#ToC_293">BETWEEN predicate</a></h3><a id="idx761" name="idx761"></a><a id="idx762" name="idx762"></a>
<a href="rbafzmstch2pred.htm#synbetween"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq398"></a>
<div class="fignone" id="wq398">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn31.htm"
border="0" /></span><a href="#skipsyn-30"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a>>>-<span class="italic">expression</span>--+-----+--BETWEEN--<span class="italic">expression</span>--AND--<span class="italic">expression</span>--->&lt;
'-NOT-'
</pre>
<a name="skipsyn-30" id="skipsyn-30"></a></div>
<a name="synbetween"></a>
<p id="synbetween">The BETWEEN predicate compares a value with a range of
values.</p>
<p>If the operands of the predicate are SBCS data, mixed data, or Unicode
data, and if the sort sequence in effect at the time the statement is executed
is not *HEX, then the comparison of the operands is performed using weighted
values for the operands. The weighted values are based on the sort sequence.</p>
<p>The BETWEEN predicate: </p>
<pre class="xmp"> value1 <span class="bold">BETWEEN</span> value2 <span class="bold">AND</span> value3</pre><p class="indatacontent"> is logically equivalent to the search condition: </p>
<pre class="xmp"> value1 >= value2 <span class="bold">AND</span> value1 &lt;= value3</pre>
<p>The BETWEEN predicate: </p>
<pre class="xmp"> value1 <span class="bold">NOT BETWEEN</span> value2 <span class="bold">AND</span> value3</pre><p class="indatacontent"> is equivalent to the search condition: </p>
<pre class="xmp"> <span class="bold">NOT</span>(value1 <span class="bold">BETWEEN</span> value2 <span class="bold">AND</span> value3);that is,
value1 &lt; value2 <span class="bold">OR</span> value1 > value3.</pre>
<p>If the operands of the BETWEEN predicate are strings with different CCSIDs,
operands are converted as if the above logically-equivalent search conditions
were specified.</p>
<p>Given a mixture of datetime values and string representations of datetime
values, all values are converted to the data type of the datetime operand.</p>
<a name="wq399"></a>
<h4 id="wq399">Examples</h4>
<pre class="xmp"><span> <tt class="xph">EMPLOYEE.SALARY <span class="bold">BETWEEN</span> 20000 <span class="bold">AND</span> 40000</tt></span>
<span> <tt class="xph">SALARY <span class="bold">NOT BETWEEN</span> 20000 + :HV1 <span class="bold">AND</span> 40000</tt></span></pre>
<a name="wq400"></a>
<h3 id="wq400"><a href="rbafzmst02.htm#ToC_295">DISTINCT predicate</a></h3><a id="idx763" name="idx763"></a><a id="idx764" name="idx764"></a>
<a href="rbafzmstch2pred.htm#syndistinct"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq401"></a>
<div class="fignone" id="wq401">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn32.htm"
border="0" /></span><a href="#skipsyn-31"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a>>>---<span class="italic">expression</span>--IS--+-----+--DISTINCT FROM--<span class="italic">expression</span>-------->&lt;
'-NOT-'
</pre>
<a name="skipsyn-31" id="skipsyn-31"></a></div>
<a name="syndistinct"></a>
<p id="syndistinct">The DISTINCT predicate compares a value with another value.</p>
<p>When the predicate is IS DISTINCT, the result of the predicate
is true if the comparison of the expressions evaluates to true. Otherwise,
the result of the predicate is false. The result cannot be unknown.</p>
<p>When the predicate IS NOT DISTINCT FROM, the result of the predicate
is true if the comparison of the expressions evaluates to true (null values
are considered equal to null values). Otherwise, the predicate is false. The
result cannot be unknown.</p>
<p>The DISTINCT predicate: </p>
<pre class="xmp"> value1 <span class="bold">IS NOT DISTINCT FROM</span> value2 </pre><p class="indatacontent"> is logically equivalent to the search condition: </p>
<pre class="xmp"> <span class="bold">(</span> value1 <span class="bold">IS NOT NULL AND</span> value2 <span class="bold">IS NOT NULL AND</span> value1 = value2 <span class="bold">)</span>
<span class="bold">OR</span>
<span class="bold">(</span> value1 <span class="bold">IS NULL AND</span> value2 <span class="bold">IS NULL )</span>
</pre>
<p>The DISTINCT predicate: </p>
<pre class="xmp"> value1 <span class="bold">IS DISTINCT FROM</span> value2 </pre><p class="indatacontent"> is logically equivalent to the search condition: </p>
<pre class="xmp"><span class="bold">NOT</span> (value1 <span class="bold">IS NOT DISTINCT FROM </span> value2) </pre>
<p>If the operands of the DISTINCT predicate are strings with different CCSIDs,
operands are converted as if the above logically-equivalent search conditions
were specified.</p>
<a name="wq402"></a>
<h4 id="wq402">Example</h4>
<p>Assume that table T1 exists and it has a single column C1, and three rows
with the following values for C1: 1, 2, null. The following query produces
the following results:</p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> T1
<span class="bold">WHERE</span> C1 <span class="bold">IS DISTINCT FROM</span> :HV</pre>
<p></p>
<a name="wq403"></a>
<table id="wq403" width="100%" summary="" border="1" frame="border" rules="all">
<thead valign="bottom">
<tr valign="bottom">
<th id="wq404" align="left">C1</th>
<th id="wq405" align="left">:HV</th>
<th id="wq406" align="left">Result</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td headers="wq404">1</td>
<td headers="wq405">2</td>
<td headers="wq406">True</td>
</tr>
<tr>
<td headers="wq404">2</td>
<td headers="wq405">2</td>
<td headers="wq406">False</td>
</tr>
<tr>
<td headers="wq404">1</td>
<td headers="wq405">Null</td>
<td headers="wq406">True</td>
</tr>
<tr>
<td headers="wq404">Null</td>
<td headers="wq405">Null</td>
<td headers="wq406">False</td>
</tr>
</tbody>
</table>
<p>The following query produces the following results:</p>
<pre class="xmp"> <span class="bold">SELECT</span> * <span class="bold">FROM</span> T1
<span class="bold">WHERE</span> C1 <span class="bold">IS NOT DISTINCT FROM</span> :HV</pre>
<p></p>
<a name="wq407"></a>
<table id="wq407" width="100%" summary="" border="1" frame="border" rules="all">
<thead valign="bottom">
<tr valign="bottom">
<th id="wq408" align="left">C1</th>
<th id="wq409" align="left">:HV</th>
<th id="wq410" align="left">Result</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td headers="wq408">1</td>
<td headers="wq409">2</td>
<td headers="wq410">False</td>
</tr>
<tr>
<td headers="wq408">2</td>
<td headers="wq409">2</td>
<td headers="wq410">True</td>
</tr>
<tr>
<td headers="wq408">1</td>
<td headers="wq409">Null</td>
<td headers="wq410">False</td>
</tr>
<tr>
<td headers="wq408">Null</td>
<td headers="wq409">Null</td>
<td headers="wq410">True</td>
</tr>
</tbody>
</table>
<a name="wq411"></a>
<h3 id="wq411"><a href="rbafzmst02.htm#ToC_297">EXISTS predicate</a></h3><a id="idx765" name="idx765"></a><a id="idx766" name="idx766"></a>
<a href="rbafzmstch2pred.htm#synexists"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq412"></a>
<div class="fignone" id="wq412">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn33.htm"
border="0" /></span><a href="#skipsyn-32"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a>>>-EXISTS--<span><span class="italic">( fullselect )</span></span>-------------------------------------->&lt;
</pre>
<a name="skipsyn-32" id="skipsyn-32"></a></div>
<a name="synexists"></a>
<p id="synexists">The EXISTS predicate tests for the existence
of certain rows. The fullselect may specify any number of columns, and </p>
<ul>
<li>The result is true only if the number of rows specified by
the fullselect is not zero.</li>
<li>The result is false only if the number of rows specified by
the fullselect is zero.</li>
<li>The result cannot be unknown.</li></ul>
<p>The values returned by the fullselect are ignored.</p>
<a name="wq413"></a>
<h4 id="wq413">Example</h4>
<pre class="xmp"> <span class="bold">EXISTS (SELECT</span> *
<span class="bold">FROM</span> EMPLOYEE <span class="bold">WHERE</span> SALARY <span class="bold">></span> 60000<span class="bold">)</span></pre>
<a name="wq414"></a>
<h3 id="wq414"><a href="rbafzmst02.htm#ToC_299">IN predicate</a></h3><a id="idx767" name="idx767"></a><a id="idx768" name="idx768"></a>
<a href="rbafzmstch2pred.htm#synin"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq415"></a>
<div class="fignone" id="wq415">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn34.htm"
border="0" /></span><a href="#skipsyn-33"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a>>>-+-<span class="italic">expression</span>--+-----+--IN--+-<span>(</span>--<span><span class="italic">fullselect</span></span>--<span>)</span>---------+-----+->&lt;
| '-NOT-' | .-,--------------. | |
| | V | | |
| +-(------<span class="italic">expression</span>---+--)-+ |
| '---<span class="italic">expression</span>-------------' |
'-<span>(</span>--<span><span class="italic">row-value-expression</span></span>--<span>)</span>--+-----+--<span>IN</span>--<span>(</span>--<span><span class="italic">fullselect</span></span>--<span>)</span>-'
'-<span>NOT</span>-'
</pre>
<a name="skipsyn-33" id="skipsyn-33"></a></div>
<a name="synin"></a>
<p id="synin">The IN predicate compares a value or values with
a set of values.</p>
<p>When a single <span class="italic">expression</span> is specified
on the left side of the operator, the IN predicate compares a value with a
set of values. When a fullselect is specified, the fullselect must return
a single result column, and can return any number of values, whether null
or not null. The data type of <span class="italic">expression</span> and the data
type of the result column of the fullselect or the <span class="italic">expression</span> on the right side of the operator must be compatible. Each variable
must identify a structure or variable that is described in accordance with
the rule for declaring host structures or variables.</p>
<p>When a <span class="italic">row-value-expression</span> is specified,
the IN predicate compares values with a collection of values. </p>
<ul>
<li>SELECT * is not allowed in the outermost select lists of the <span class="italic">fullselect</span>.</li>
<li>The result table of the <span class="italic">fullselect</span> must have the
same number of columns as the <span class="italic">row-value-expression</span>.
The data types of the corresponding expressions of the <span class="italic">row-value-expression</span> and the <span class="italic">fullselect</span> must
be compatible. The value of each expression on the left side is compared with
the value of its corresponding expression on the right side.</li></ul>
<p>The value of the predicate depends on the operator that is specified:</p>
<ul>
<li>When the operator is IN, the result of the predicate is:
<ul>
<li>True if at least one row returned from the fullselect is equal to the <span class="italic">row-value-expression</span>.</li>
<li>False if the result of the fullselect is empty or if no row returned from
the fullselect is equal to the <span class="italic">row-value-expression</span>.</li>
<li>Otherwise, unknown (that is, if the comparison of <span class="italic">row-value-expression</span> to the row returned from the fullselect evaluates
to unknown because of a null value for at least one row returned from the
fullselect and no row returned from the fullselect is equal to the <span class="italic">row-value-expression</span>).</li></ul></li>
<li>When the operator is NOT IN, the result of the predicate is:
<ul>
<li>True if the result of the fullselect is empty or if the <span class="italic">row-value-expression</span> is not equal to any of the rows returned by the
fullselect.</li>
<li>False if the <span class="italic">row-value-expression</span> is equal to
at least one row returned by the fullselect.</li>
<li>Otherwise, unknown (that is, if the comparison of <span class="italic">row-value-expression</span> to the row returned from the fullselect evaluates
to unknown because of a null value for at least one row returned from the
fullselect and the comparison of <span class="italic">row-value-expression</span> to
the row returned from the fullselect is not true for any row returned by the
fullselect).</li></ul></li></ul>
<p>If the corresponding operands of the predicate are SBCS data, mixed data,
or Unicode data, and if the sort sequence in effect at the time the statement
is executed is not *HEX, then the comparison of the operands is performed
using weighted values for the operands. The weighted values are based on the
sort sequence.</p>
<p>An IN predicate is equivalent to other predicates as follows:</p>
<a name="wq416"></a>
<table id="wq416" width="100%" summary="" border="0" frame="void" rules="all">
<thead valign="bottom">
<tr valign="bottom">
<th id="wq417" align="left">IN predicate</th>
<th id="wq418" align="left">Equivalent predicate</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td headers="wq417">expression <span class="bold">IN</span> <span class="bold">(</span>expression<span class="bold">)</span></td>
<td headers="wq418">expression <span class="bold">=</span> expression</td>
</tr>
<tr>
<td headers="wq417">expression <span class="bold">IN (</span>fullselect<span class="bold">)</span></td>
<td headers="wq418">expression <span class="bold">= ANY (</span>fullselect<span class="bold">)</span></td>
</tr>
<tr>
<td headers="wq417">expression <span class="bold">NOT IN (</span>fullselect<span class="bold">)</span></td>
<td headers="wq418">expression <span class="bold">&lt;> ALL (</span>fullselect<span class="bold">)</span></td>
</tr>
<tr>
<td headers="wq417">expression <span class="bold">IN (</span>value1, value2,
..., valuen<span class="bold">)</span></td>
<td headers="wq418">expression <span class="bold">IN (SELECT</span> * <span class="bold">FROM</span> R<span class="bold">)</span>
<p></p>Where T is a table with a single
row and R is a temporary table formed by the following fullselect:
<pre class="xmp"> <span class="bold">SELECT</span> value1 <span class="bold">FROM</span> T
<span class="bold">UNION</span>
<span class="bold">SELECT</span> value2 <span class="bold">FROM</span> T
<span class="bold">UNION</span>
.
.
.
<span class="bold">UNION</span>
<span class="bold">SELECT</span> valuen <span class="bold">FROM</span> T</pre></td>
</tr>
<tr>
<td headers="wq417">row-value-expression <span class="bold">IN (</span>fullselect<span class="bold">)</span></td>
<td headers="wq418">row-value-expression <span class="bold">= SOME (</span> fullselect<span class="bold">)</span></td>
</tr>
<tr>
<td headers="wq417">row-value-expression <span class="bold">IN (</span>fullselect<span class="bold">)</span></td>
<td headers="wq418">row-value-expression <span class="bold">= ANY (</span> fullselect<span class="bold">)</span></td>
</tr>
<tr>
<td headers="wq417">row-value-expression <span class="bold">NOT IN (</span>fullselect<span class="bold">)</span></td>
<td headers="wq418">row-value-expression <span class="bold">&lt;> ALL (</span> fullselect<span class="bold">)</span></td>
</tr>
</tbody>
</table>
<p>If the operands of the IN predicate have different data types or attributes,
the rules used to determine the data type for evaluation of the IN predicate
are those for UNION, UNION ALL, EXCEPT, and INTERSECT. For a description,
see <a href="rbafzmstopcomb.htm#opcomb">Rules for result data types</a>.</p>
<p>If the operands of the IN predicate are strings with different CCSIDs,
the rules used to determine which operands are converted are those for operations
that combine strings. For a description, see <a href="rbafzmstuuall.htm#uuall">Conversion rules for operations that combine strings</a>.</p>
<a name="wq419"></a>
<h4 id="wq419">Examples</h4>
<p></p>
<pre class="xmp"> DEPTNO <span class="bold">IN (</span>'D01', 'B01', 'C01'<span class="bold">)</span>
EMPNO <span class="bold">IN(SELECT</span> EMPNO <span class="bold">FROM</span> EMPLOYEE <span class="bold">WHERE</span> WORKDEPT = 'E11'<span class="bold">)</span></pre>
<a name="ch2like"></a>
<h3 id="ch2like"><a href="rbafzmst02.htm#ToC_301">LIKE predicate</a></h3><a id="idx769" name="idx769"></a><a id="idx770" name="idx770"></a>
<a href="rbafzmstch2pred.htm#synlike"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq420"></a>
<div class="fignone" id="wq420">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn35.htm"
border="0" /></span><a href="#skipsyn-34"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a>>>-<span class="italic">match-expression</span>--+-----+--LIKE--<span class="italic">pattern-expression</span>--+---------------------------+->&lt;
'-NOT-' '-ESCAPE--<span class="italic">escape-expression</span>-'
</pre>
<a name="skipsyn-34" id="skipsyn-34"></a></div>
<a name="synlike"></a>
<p id="synlike">The LIKE predicate searches for strings that have a certain
pattern. The pattern is specified by a string in which the underscore and
percent sign have special meanings. Trailing blanks in a pattern are a part
of the pattern.</p>
<p>If the value of any of the arguments is null, the result of the LIKE predicate
is unknown.</p>
<p>The <span class="italic">match-expression</span>, <span class="italic">pattern-expression</span>, and <span class="italic">escape-expression</span> must identify strings
or numbers. A numeric argument is cast to a character string before evaluating
the predicate. For more information on converting numeric to a character string,
see <a href="rbafzmstscale.htm#scavarchar">VARCHAR</a>. The values for <span class="italic">match-expression</span>, <span class="italic">pattern-expression</span>, and <span class="italic">escape-expression</span> must either all be binary strings or none can be binary
strings. The three arguments can include a mixture of character strings and
graphic strings.</p>
<p>None of the expressions can yield a distinct type. However, it can be a
function that casts a distinct type to its source type.</p>
<p>If the operands of the predicate are SBCS data, mixed data, or Unicode
data, and if the sort sequence in effect at the time the statement is executed
is not *HEX, then the comparison of the operands is performed using weighted
values for the operands. The weighted values are based on the sort sequence.
An ICU sort sequence is not allowed with a LIKE predicate.</p>
<p>With character strings, the terms <span class="italic">character</span>, <span class="italic">percent sign</span>, and <span class="italic">underscore</span> in
the following discussion refer to single-byte characters. With graphic strings,
the terms refer to double-byte or Unicode characters. With binary strings,
the terms refer to the code points of those single-byte characters.</p>
<dl class="parml">
<dt class="bold"><span class="italic">match-expression</span></dt>
<dd>An expression that specifies the string that is to be examined to see
if it conforms to a certain pattern of characters.
</dd>
<dt class="bold">LIKE <span class="italic">pattern-expression</span></dt>
<dd>An expression that specifies the string that is to be matched.
<p><span class="bold">Simple description</span>: A simple description of the LIKE pattern
is as follows: </p>
<ul>
<li>The underscore sign (_) represents any single character. <a id="idx771" name="idx771"></a></li>
<li>The percent sign (%) represents a string of zero or more <a id="idx772" name="idx772"></a>characters.</li>
<li>Any other character represents itself.</li></ul>
<p>If the <span class="italic">pattern-expression</span> needs to include
either the underscore or the percent character, the <span class="italic">escape-expression</span> is used to specify a character to precede either the underscore or percent
character in the pattern.</p>
<p><span class="bold">Rigorous description</span>:
Let <var class="pv">x</var> denote a value of <var class="pv">match-expression</var> and <var class="pv">y</var> denote
the value of <var class="pv">pattern-expression</var>.</p>
<p>The string <var class="pv">y</var> is
interpreted as a sequence of the minimum number of substring specifiers so
each character of <var class="pv">y</var> is part of exactly one substring specifier. A
substring specifier is an underscore, a percent sign, or any nonempty sequence
of characters other than an underscore or a percent sign.</p>
<p>The result
of the predicate is unknown if <var class="pv">x</var> or <var class="pv">y</var> is the null value.
Otherwise, the result is either true or false. The result is true if <var class="pv">x</var> and <var class="pv">y</var> are both empty strings or if there exists a partitioning
of <var class="pv">x</var> into substrings such that: </p>
<ul>
<li>A substring of <var class="pv">x</var> is a sequence of zero or more contiguous characters
and each character of <var class="pv">x</var> is part of exactly one substring.</li>
<li>If the <var class="pv">n</var>th substring specifier is an underscore, the <var class="pv">n</var>th
substring of <var class="pv">x</var> is any single character.</li>
<li>If the <var class="pv">n</var>th substring specifier is a percent sign, the <var class="pv">n</var>th
substring of <var class="pv">x</var> is any sequence of zero or more characters.</li>
<li>If the <var class="pv">n</var>th substring specifier is neither an underscore nor a
percent sign, the <var class="pv">n</var>th substring of <var class="pv">x</var> is equal to that substring
specifier and has the same length as that substring specifier.</li>
<li>The number of substrings of <var class="pv">x</var> is the same as the number of substring
specifiers.</li></ul>
<p>It follows that if <var class="pv">y</var> is an empty string and <var class="pv">x</var> is
not an empty string, the result is false. Similarly, it follows that if <var class="pv">y</var> is an empty string and <var class="pv">x</var> is not an empty string consisting
of other than percent signs, the result is false.</p>
<p>The predicate <var class="pv">x</var><tt class="xph"> NOT LIKE </tt><var class="pv">y</var> is equivalent to the search condition <tt class="xph">NOT(<var class="pv">x</var> LIKE <var class="pv">y</var>)</tt>.</p>
<p>If necessary, the CCSID of the <span class="italic">match-expression</span>, <span class="italic">pattern-expression</span>, and <span class="italic">escape-expression</span> are converted to the
compatible CCSID between the <span class="italic">match-expression</span> and <span class="italic">pattern-expression</span>.</p>
<p><span class="bold">Mixed data</span>: If the column is mixed data, the pattern can include both SBCS and
DBCS characters. The special characters in the pattern are interpreted as
follows: </p>
<ul>
<li>An SBCS underscore refers to one SBCS character.</li>
<li>A DBCS underscore refers to one DBCS character.</li>
<li>A percent sign (either SBCS or DBCS) refers to any number of characters
of any type, either SBCS or DBCS.</li>
<li>Redundant shifts in <span class="italic">match-expression</span> and <span class="italic">pattern-expression</span> are ignored.<sup class="fn"><a id="wq421" name="wq421" href="rbafzmstch2pred.htm#wq422">39</a></sup></li></ul><a id="idx773" name="idx773"></a><a id="idx774" name="idx774"></a><a id="idx775" name="idx775"></a>
<p><span class="bold">Unicode
data</span>: For Unicode, the special characters in the pattern are interpreted
as follows: </p>
<ul>
<li>An SBCS or DBCS underscore refers to one character (a character can be
one or more bytes)</li>
<li>A percent sign (either SBCS or DBCS) refers to a string of zero or more
characters (a character can be one or more bytes).</li></ul><p class="indatacontent"> When the LIKE predicate is used with Unicode data, the Unicode percent
sign and underscore use the code points indicated in the following table: </p>
<a name="wq423"></a>
<table id="wq423" width="100%" summary="" border="1" frame="hsides" rules="all">
<caption>Table 26. </caption>
<thead valign="bottom">
<tr>
<th id="wq424" width="33%" align="left" valign="top">Character</th>
<th id="wq425" width="33%" align="left" valign="top">UTF-8</th>
<th id="wq426" width="33%" align="left" valign="top">UTF-16 or UCS-2</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td headers="wq424">Half-width %</td>
<td headers="wq425">X'25'</td>
<td headers="wq426">X'0025'</td>
</tr>
<tr>
<td headers="wq424">Full-width %</td>
<td headers="wq425">X'EFBC85'</td>
<td headers="wq426">X'FF05'</td>
</tr>
<tr>
<td headers="wq424">Half-width _</td>
<td headers="wq425">X'5F'</td>
<td headers="wq426">X'005F'</td>
</tr>
<tr>
<td headers="wq424">Full-width _</td>
<td headers="wq425">X'EFBCBF'</td>
<td headers="wq426">X'FF3F'</td>
</tr>
</tbody>
</table><p class="indatacontent"> The full-width or half-width % matches zero or more characters. The
full-width or half width _ character matches exactly one character. (For EBCDIC
data, a full-width _ character matches one DBCS character.)</p>
<a name="likepatfl"></a>
<p id="likepatfl"><span class="bold">Parameter marker</span>:</p>
<p>When the pattern specified in a
LIKE predicate is a parameter marker, and a fixed-length character variable
is used to replace the parameter marker; specify a value for the variable
that is the correct length. If a correct length is not specified, the select
will not return the intended results.</p>
<p>For example, if the variable is
defined as CHAR(10), and the value WYSE% is assigned to that variable, the
variable is padded with blanks on assignment. The pattern used is </p>
<pre class="xmp"> 'WYSE% '</pre>
<p>This pattern requests the database manager to search for all
values that start with WYSE and end with five blank spaces. If you intended
to search for only the values that start with 'WYSE' you should assign the
value 'WYSE%%%%%%' to the variable.</p>
</dd>
<dt class="bold">ESCAPE <span class="italic">escape-expression</span></dt><a id="idx776" name="idx776"></a>
<dd>An expression that specifies a character to be used to modify the special
meaning of the underscore (_) and percent (%) characters in the pattern-expression.
This allows the LIKE predicate to be used to match values that contain the
actual percent and underscore characters. The following rules apply the use
of the ESCAPE clause and the <span class="italic">escape-expression</span>:
<ul>
<li>The <span class="italic">escape-expression</span> must be a string of length
1.<sup class="fn"><a id="wq427" name="wq427" href="rbafzmstch2pred.htm#wq428">40</a></sup></li>
<li>The <span class="italic">pattern-expression</span> must not contain the escape
character except when followed by the escape character, percent, or underscore.
<p>For example, if '+' is the escape character, any occurrences of '+'
other than '++', '+_', or '+%' in the <span class="italic">pattern-expression</span> is an error.</p></li>
<li>The <span class="italic">escape-expression</span> can be a parameter marker.</li></ul>
<p>The following example shows the effect of successive occurrences of
the escape character, which in this case is the plus sign (+).</p>
<a name="wq429"></a>
<table id="wq429" width="100%" summary="" border="0" frame="void" rules="all">
<thead valign="bottom">
<tr valign="bottom">
<th id="wq430" width="37%" align="left">When the pattern string is...</th>
<th id="wq431" width="62%" align="left">The actual pattern is...</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td headers="wq430">+%</td>
<td headers="wq431">A percent sign</td>
</tr>
<tr>
<td headers="wq430">++%</td>
<td headers="wq431">A plus sign followed by zero or
more arbitrary characters</td>
</tr>
<tr>
<td headers="wq430">+++%</td>
<td headers="wq431">A plus sign followed by a percent
sign</td>
</tr>
</tbody>
</table>
</dd>
</dl>
<a name="wq432"></a>
<h4 id="wq432">Examples</h4>
<a name="wq433"></a>
<h5 id="wq433">Example 1</h5>
<p>Search for the string 'SYSTEMS' appearing anywhere within the PROJNAME
column in the PROJECT table. </p>
<pre class="xmp"> <span class="bold">SELECT</span> PROJNAME
<span class="bold">FROM</span> PROJECT
<span class="bold">WHERE</span> PROJECT.PROJNAME <span class="bold">LIKE</span> '%SYSTEMS%'</pre>
<a name="wq434"></a>
<h5 id="wq434">Example 2</h5>
<p>Search for a string with a first character of 'J' that is exactly
two characters long in the FIRSTNME column of the EMPLOYEE table. </p>
<pre class="xmp"><span class="bold">SELECT</span> FIRSTNME
<span class="bold">FROM</span> EMPLOYEE
<span class="bold">WHERE</span> EMPLOYEE.FIRSTNME <span class="bold">LIKE</span> 'J_'</pre>
<a name="wq435"></a>
<h5 id="wq435">Example 3</h5>
<p>In this example: </p>
<pre class="xmp"><span class="bold">SELECT *</span>
<span class="bold">FROM</span> TABLEY
<span class="bold">WHERE</span> C1 <span class="bold">LIKE</span> 'AAAA+%BBB%' <span class="bold">ESCAPE</span> '+'</pre><p class="indatacontent">'+' is the escape character and
indicates that the search is for a string that starts with 'AAAA%BBB'.
The '+%' is interpreted as a single occurrence of '%' in the
pattern.</p>
<a name="wq436"></a>
<h5 id="wq436">Example 4</h5>
<p>Assume that a distinct type named ZIP_TYPE with a source data type of CHAR(5)
exists and an ADDRZIP column with data type ZIP_TYPE exists in some table
TABLEY. The following statement selects the row if the zip code (ADDRZIP)
begins with '9555'.</p>
<pre class="xmp"> <span class="bold">SELECT *</span>
<span class="bold">FROM</span> TABLEY
<span class="bold">WHERE CHAR(</span>ADDRZIP<span class="bold">) LIKE</span> '9555%'</pre>
<a name="wq437"></a>
<h5 id="wq437">Example 5</h5>
<p>The RESUME column in sample table EMP_RESUME is defined as a CLOB. If the
variable LASTNAME has a value of 'JONES', the following statement selects
the RESUME column when the string JONES appears anywhere in the column.</p>
<pre class="xmp"> <span class="bold">SELECT</span> RESUME
<span class="bold">FROM</span> EMP_RESUME
<span class="bold">WHERE</span> RESUME <span class="bold">LIKE</span> '%'||LASTNAME||'%'</pre>
<a name="wq438"></a>
<h5 id="wq438">Example 6</h5>
<p>In the following table of EBCDIC examples, assume COL1 is mixed data. The
table shows the results when the predicates in the first column are evaluated
using the COL1 values from the second column: </p>
<a name="wq439"></a>
<div class="fignone" id="wq439">
<div class="mmobj">
<img src="rv3f001.gif" alt="Results when the predicates in the first column are evaluated using the COL1 values from the second column. Where predicate 'aaa Shift-out ABC%C Shift-in' compared to 'aaa Shift-out ABCZC Shift-in' returns true. Where predicate 'aaa Shift-out ABC Shift-in % Shift-out C Shift-in' compared to 'aaa Shift-out ABC Shift-in drz Shift-out C Shift-in' returns true. Where predicate 'a% Shift-out C Shift-in' compared to 'a Shift-out C Shift-in', 'ax Shift-out C Shift-in', and 'ab Shift-out DE Shift-in fg Shift-out C Shift-in' all return true. Where 'a_Shift-out C Shift-in' compared to 'a% Shift-out C Shift-in' returns true and 'a Shift-out XC Shift-in' returns false. Where 'a Shift-out __C Shift-in' compared to 'a Shift-out XC Shift-in' returns true and 'ax Shift-out C Shift-in' returns false. Where ''Shift-out Shift-in' compared to an empty string returns true. Where 'ab Shift-out C Shift-in_' compared to 'ab Shift-out C Shift-in d' and 'ab Shift-out Shift-in Shift-out C Shift-in' return true." /></div></div>
<a name="wq440"></a>
<h3 id="wq440"><a href="rbafzmst02.htm#ToC_309">NULL predicate</a></h3><a id="idx777" name="idx777"></a><a id="idx778" name="idx778"></a>
<a href="rbafzmstch2pred.htm#synnull"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
<a name="wq441"></a>
<div class="fignone" id="wq441">
<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn36.htm"
border="0" /></span><a href="#skipsyn-35"><img src="c.gif" alt="Skip visual syntax diagram"
border="0" /></a>>>-<span class="italic">expression</span>--IS--+-----+--NULL------------------------------->&lt;
'-NOT-'
</pre>
<a name="skipsyn-35" id="skipsyn-35"></a></div>
<a name="synnull"></a>
<p id="synnull">The NULL predicate tests for null values.</p>
<p>The result of a NULL predicate cannot be unknown. If the value of the expression
is null, the result is true. If the value is not null, the result is false.</p>
<p>If NOT is specified, the result is reversed.</p>
<a name="wq442"></a>
<h4 id="wq442">Examples</h4>
<p></p>
<pre class="xmp"> EMPLOYEE.PHONE <span class="bold">IS NULL</span>
SALARY <span class="bold">IS NOT NULL</span></pre>
<hr /><div class="fnnum"><a id="wq422" name="wq422" href="rbafzmstch2pred.htm#wq421">39</a>.</div>
<div class="fntext">Redundant shifts are normally ignored.
To guarantee that they are ignored, however, specify the IGNORE_LIKE_REDUNDANT_SHIFTS
query attribute. See <a href="../rzajq/rzajqkickoff.htm">Database Performance and Query Optimization</a> for information on setting query attributes.</div><div class="fnnum"><a id="wq428" name="wq428" href="rbafzmstch2pred.htm#wq427">40</a>.</div>
<div class="fntext">If it is NUL-terminated, a C character string variable of length 2 can
be specified.</div>
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