C Language and Host Variables
This section lists the requirements and limits for using host variables in a C program.
Any valid C host variable is permissible in a SQL statement. All variables are not valid, however. Host variables must meet certain requirements before PP2 accepts them in SQL statements. See Host Variable Declaration.
Any valid C variable name can be used as a host variable name, including names with embedded underscores ( _ ).
SQL and Host Variables
Declare host variables that will be used in SQL statements (that is, enclose host variables between BEGIN DECLARE/END DECLARE statements). Multiple declare sections are permissible. Variables declared elsewhere are not considered valid for SQL usage by PP2.
BEGIN DECLARE and END DECLARE are documented in “Embedded SQL” in Teradata Vantage™ - SQL Stored Procedures and Embedded SQL , B035-1148 .
Variable names used in SQL requests are case sensitive; for example, VAR1 is not equivalent to var1. Dynamic SQL, when executed in Teradata mode, returns a designation of character (452 or 453) to the SQLDA structure when a PREPARE...INTO or DESCRIBE is performed and no null terminator is supplied when the data is returned to the field.
Host variables that are not SQL strings represent data values only: they cannot be used to represent database, table, view, macro, or column names.
Indicator Variables
Use the form short [int] var1[x] only as an indicator array with a structure reference.
PP2 Issues
PP2 expects a terminating null character (‘\0’) on input and terminates the string with a ‘\0’ on output when used with a static request.
Change the type designation in the application to receive a null terminated field.
Declare a host variable as a variable character field by using the PP2 directive VARCHAR. This designation is replaced by a structure when the C code is generated.
Any terminating null is treated as part of the string, both when used as input and as output. For details, see "Varying Character Data" in Server to Host Assignment.
Host Variable Declaration
Use the following C type specifiers and declarations to define a host variable declaration:
auto char double extern float int long short static struct (excluding tag type definitions) unsigned char
A host variable that is defined as a “long” data type will be 4 bytes when compiled with the 32-bit compiler option and 8 bytes when compiled with the 64-bit compiler options on the Solaris, AIX or 64-bit Windows platforms.
- SQLTYPE to the INTEGER data type
- SQLLEN to “sizeof(long)”
The following C type specifiers and declarations cannot be used to declare a host variable:
#define enum pointer designation (char *var1) register structure definition via tags typedef union unsigned integer types void
Specify C array dimensions by a numeric literal. Defined constants or numeric expressions are not allowed within a C array declaration.