Use ILE C compiler external file descriptions in C and C++ applications that use SQL

You can use the C or C++ #pragma mapinc directive with the #include directive to include external file descriptions in your program.

When used with SQL, only a particular format of the #pragma mapinc directive is recognized by the SQL precompiler. If all of the required elements are not specified, the precompiler ignores the directive and does not generate host variable structures. The required elements are:

Include name
Externally described file name
Format name or a list of format names
Options
Conversion options

The library name, union name, conversion options, and prefix name are optional. Although typedef statements coded by the user are not recognized by the precompiler, those created by the #pragma mapinc and #include directives are recognized. SQL supports input, output, both, and key values for the options parameter. For the conversion options, the supported values are D, p, z, _P, and 1BYTE_CHAR. These options may be specified in any order except that both D and p cannot be specified. Unions declared using the typedef union created by the #pragma mapinc and #include directive cannot be used as host variables in SQL statements; the members of the unions can be used. Structures that contain the typedef structure cannot be used in SQL statements; the structure declared using the typedef can be used.

To retrieve the definition of the sample table DEPARTMENT described in DB2^® UDB for iSeries™ sample tables in the DB2 UDB for iSeries SQL Programming topic collection, you can code the following:

    #pragma mapinc ("dept","CORPDATA/DEPARTMENT(*ALL)","both")
    #include "dept"
    CORPDATA_DEPARTMENT_DEPARTMENT_both_t Dept_Structure;

A host structure named Dept_Structure is defined with the following elements: DEPTNO, DEPTNAME, MGRNO, and ADMRDEPT. These field names can be used as host variables in SQL statements.

Note: DATE, TIME, and TIMESTAMP columns generate character host variable definitions. They are treated by SQL with the same comparison and assignment rules as a DATE, TIME, and TIMESTAMP column. For example, a date host variable can only compared against a DATE column or a character string which is a valid representation of a date.

If the GRAPHIC or VARGRAPHIC column has a UCS-2 CCSID, the generated host variable will have the UCS-2 CCSID assigned to it. If the GRAPHIC or VARGRAPHIC column has a UTF-16 CCSID, the generated host variable will have the UTF-16 CCSID assigned to it.

Although zoned, binary (with non-zero scale fields), and optionally decimal are mapped to character fields in ILE C for iSeries, SQL will treat these fields as numeric. By using the extended program model (EPM) routines, you can manipulate these fields to convert zoned and packed decimal data. For more information, see the ILE C for iSeries Language Reference Link to PDF topic.