Code SQL statements in C and C++ applications

This topic describes the unique application and coding requirements for embedding SQL statements in a C or C++ program.

C program refers to ILE C for iSeries™ programs. C++ program refers to ILE C++ programs. This topic also defines the requirements for host structures and host variables. For more details, see the following sections:

• Define the SQL communications area in C and C++ applications that use SQL
  A C or C++ program can be written to use the SQLCA to check return status for embedded SQL statements, or the program can use the SQL diagnostics area to check return status.
• Define SQL descriptor areas in C and C++ applications that use SQL
  There are two types of SQL descriptor areas. One is defined with the ALLOCATE DESCRIPTOR statement. The other is defined using the SQL descriptor area (SQLDA) structure. In this topic, only the SQLDA form is discussed.
• Embed SQL statements in C and C++ applications that use SQL
  SQL statements can be coded in a C or C++ program wherever executable statements can appear.
• Use host variables in C and C++ applications that use SQL
  All host variables used in SQL statements must be explicitly declared prior to their first use.
• Use host structures in C and C++ applications that use SQL
  In C and C++ programs, you can define a host structure, which is a named set of elementary C or C++ variables.
• Use arrays of host structures in C and C++ applications that use SQL
  In C and C++ programs, you can define a host structure array that has the dimension attribute. Host structure arrays have a maximum of two levels, even though the array might occur within a multiple-level structure. Another structure is not needed if a varying-length character string or a varying-length graphic string is not used.
• Use pointer data types in C and C++ applications that use SQL
  You can also declare host variables that are pointers to the supported C and C++ data types, with the following restrictions.
• Use typedef in C and C++ applications that use SQL
  You can also use the typedef declarations to define your own identifiers that will be used in place of C type specifiers such as short, float, and double.
• 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.
• Determine equivalent SQL and C or C++ data types
  The precompiler determines the base SQLTYPE and SQLLEN of host variables based on the following table. If a host variable appears with an indicator variable, the SQLTYPE is the base SQLTYPE plus one.
• Use indicator variables in C and C++ applications that use SQL
  An indicator variable is a two-byte integer (short int).