103 lines
5.8 KiB
HTML
103 lines
5.8 KiB
HTML
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<meta name="abstract" content="In C and C++ programs, you can define a host structure, which is a named set of elementary C or C++ variables." />
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<title>Use host structures in C and C++ applications that use SQL</title>
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</head>
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<body id="rzajphoststrucc"><a name="rzajphoststrucc"><!-- --></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 structures in C and C++ applications that use SQL</h1>
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<div><p>In C and C++ programs, you can define a <em>host structure</em>,
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which is a named set of elementary C or C++ variables.</p>
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<div class="section"><p>Host structures have a maximum of two levels, even though the
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host structure might itself occur within a multilevel structure. An exception
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is the declaration of a varying-length string, which requires another structure.</p>
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</div>
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<div class="section"><p>A host structure name can be a group name whose subordinate levels
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name elementary C or C++ variables. For example: </p>
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<pre> struct {
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struct {
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char c1;
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char c2;
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} b_st;
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} a_st;</pre>
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</div>
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<div class="section"><p>In this example, b_st is the name of a host structure consisting
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of the elementary items c1 and c2.</p>
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</div>
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<div class="section"><p>You can use the structure name as a shorthand notation for a list
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of scalars, but only for a two-level structure. You can qualify a host variable
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with a structure name (for example, structure.field). Host structures are
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limited to two levels. (For example, in the above host structure example,
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the a_st cannot be referred to in SQL.) A structure cannot contain an intermediate
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level structure. In the previous example, a_st could not be used as a host
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variable or referred to in an SQL statement. A host structure for SQL data
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has two levels and can be thought of as a named set of host variables. After
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the host structure is defined, you can refer to it in an SQL statement instead
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of listing the several host variables (that is, the names of the host variables
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that make up the host structure).</p>
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</div>
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<div class="section"><p>For example, you can retrieve all column values from selected
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rows of the table CORPDATA.EMPLOYEE with: </p>
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<pre> struct { char empno[7];
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struct { short int firstname_len;
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char firstname_text[12];
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} firstname;
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char midint,
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struct { short int lastname_len;
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char lastname_text[15];
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} lastname;
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char workdept[4];
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} pemp1;
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.....
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strcpy("000220",pemp1.empno);
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.....
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exec sql
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<strong>SELECT</strong> *
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<strong>INTO</strong> :pemp1
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<strong>FROM</strong> corpdata.employee
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<strong>WHERE</strong> empno=:pemp1.empno;</pre>
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</div>
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<div class="section"><p>Notice that in the declaration of pemp1, two varying-length string
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elements are included in the structure: firstname and lastname.</p>
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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="rzajphoststrucdeclaration.htm">Host structure declarations in C and C++ applications that use SQL</a></strong><br />
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These figures show the valid syntax for host structure declarations.</li>
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<li class="ulchildlink"><strong><a href="rzajphoststrucindicator.htm">Host structure indicator array in C and C++ applications that use SQL</a></strong><br />
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This figure shows the valid syntax for host structure indicator array declarations.</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="rzajpc.htm" title="This topic describes the unique application and coding requirements for embedding SQL statements in a C or C++ program.">Code SQL statements in C and C++ applications</a></div>
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</div>
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