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<title>Use host variables in SQL statements</title>
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</head>
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<body id="rzajphostvar"><a name="rzajphostvar"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Use host variables in SQL statements</h1>
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<div><p>When your program retrieves data, the values are put into data
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items defined by your program and specified with the INTO clause of a SELECT
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INTO or FETCH statement. The data items are called <em>host variables</em>.</p>
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<div class="section"><p>A host variable is a field in your program that is specified in
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an SQL statement, usually as the source or target for the value of a column.
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The host variable and column must be data type compatible. Host variables
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may not be used to identify SQL objects, such as tables or views, except in
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the DESCRIBE TABLE statement.</p>
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</div>
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<div class="section"><div class="p">A <strong>host structure</strong> is a group of host variables used as the
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source or target for a set of selected values (for example, the set of values
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for the columns of a row). A <strong>host structure array</strong> is an array of host
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structures used in the multiple-row FETCH and blocked INSERT statements. <div class="note"><span class="notetitle">Note:</span> By
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using a host variable instead of a literal value in an SQL statement, you
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give the application program the flexibility it needs to process different
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rows in a table or view.</div>
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</div>
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</div>
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<div class="section"><p>For example, instead of coding an actual department number in
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a WHERE clause, you can use a host variable set to the department number you
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are currently interested in.</p>
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</div>
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<div class="section"><p>Host variables are commonly used in SQL statements in these ways: </p>
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</div>
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<div class="section"> <ul><li><strong>In a WHERE clause:</strong> You can use a host variable to specify a value
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in the predicate of a search condition, or to replace a literal value in an
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expression. For example, if you have defined a field called EMPID that contains
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an employee number, you can retrieve the name of the employee whose number
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is 000110 with: <pre> MOVE '000110' TO EMPID.
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EXEC SQL
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<strong>SELECT</strong> LASTNAME
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<strong>INTO</strong> :PGM-LASTNAME
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> EMPNO = :EMPID
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END-EXEC.</pre>
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</li>
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<li><strong>As a receiving area for column values (named in an INTO clause):</strong> You
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can use a host variable to specify a program data area that is to contain
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the column values of a retrieved row. The INTO clause names one or more host
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variables that you want to contain column values returned by SQL. For example,
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suppose you are retrieving the <em>EMPNO</em>, <em>LASTNAME</em>, and <em>WORKDEPT</em> column
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values from rows in the CORPDATA.EMPLOYEE table. You could define a host variable
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in your program to hold each column, then name the host variables with an
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INTO clause. For example: <pre> EXEC SQL
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<strong>SELECT</strong> EMPNO, LASTNAME, WORKDEPT
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<strong>INTO</strong> :CBLEMPNO, :CBLNAME, :CBLDEPT
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> EMPNO = :EMPID
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END-EXEC.</pre>
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<p>In this example, the host variable CBLEMPNO receives
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the value from EMPNO, CBLNAME receives the value from LASTNAME, and CBLDEPT
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receives the value from WORKDEPT.</p>
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</li>
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<li><strong>As a value in a SELECT clause:</strong> When specifying a list of items
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in the SELECT clause, you are not restricted to the column names of tables
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and views. Your program can return a set of column values intermixed with
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host variable values and literal constants. For example: <pre> MOVE '000220' TO PERSON.
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EXEC SQL
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<strong>SELECT</strong> "A", LASTNAME, SALARY, :RAISE,
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SALARY + :RAISE
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<strong>INTO</strong> :PROCESS, :PERSON-NAME, :EMP-SAL,
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:EMP-RAISE, :EMP-TTL
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> EMPNO = :PERSON
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END-EXEC.</pre>
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<p>The results are: </p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="90%" frame="hsides" border="1" rules="all"><thead align="left"><tr><th align="left" valign="bottom" width="14.25925925925926%" id="d0e154">PROCESS</th>
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<th align="left" valign="bottom" width="42.77777777777778%" id="d0e156">PERSON-NAME</th>
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<th align="left" valign="bottom" width="14.25925925925926%" id="d0e158">EMP-SAL</th>
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<th align="left" valign="bottom" width="14.25925925925926%" id="d0e160">EMP-RAISE</th>
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<th align="left" valign="bottom" width="14.444444444444443%" id="d0e162">EMP-TTL</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="14.25925925925926%" headers="d0e154 ">A</td>
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<td align="left" valign="top" width="42.77777777777778%" headers="d0e156 ">LUTZ</td>
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<td align="left" valign="top" width="14.25925925925926%" headers="d0e158 ">29840</td>
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<td align="left" valign="top" width="14.25925925925926%" headers="d0e160 ">4476</td>
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<td align="left" valign="top" width="14.444444444444443%" headers="d0e162 ">34316</td>
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</tr>
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</tbody>
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</table>
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</div>
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</li>
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<li><strong>As a value in other clauses of an SQL statement:</strong> <ul><li>The SET clause in an UPDATE statement</li>
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<li>The VALUES clause in an INSERT statement</li>
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<li>The CALL statement</li>
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</ul>
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</li>
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</ul>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzajpasnrule.htm">Assignment rules for host variables in SQL statements</a></strong><br />
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SQL values are assigned to host variables during the running of FETCH, SELECT INTO, SET, and VALUES INTO statements. SQL values are assigned from host variables during the running of INSERT, UPDATE, and CALL statements.</li>
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<li class="ulchildlink"><strong><a href="rzajpindvar.htm">Indicator variables in applications that use SQL</a></strong><br />
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An <em>indicator variable</em> is a halfword integer variable used
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to indicate whether its associated host variable has been assigned a null
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value.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajpsqlcom.htm" title="This topic describes some concepts and rules that are common to using SQL statements in a host language.">Common concepts and rules for using embedded SQL</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../db2/rbafzmst02.htm">SQL reference</a></div>
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</div>
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</div>
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</body>
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</html>
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