Rules for Coding Host-Variables in C

CA Datacom/DB SQL Preprocessors › Embedding SQL Statements in Host Programs › Coding Embedded SQL in C › Rules for Coding Host-Variables in C

Rules for Coding Host-Variables in C

When you code host-variable declarations in C, you must comply with the following requirements:

Host and indicator variables must be within the scope of the referencing SQL statement.
In ANSI mode, host and indicator variables must be within the BEGIN and END DECLARE SECTION. Multiple DECLARE sections are allowed. That is, in C only host variables that are declared within an EXEC SQL BEGIN DECLARE SECTION/EXEC SQL END DECLARE SECTION are valid.
Note: The SQLWAs and SQLCA are automatically generated after the first EXEC SQL BEGIN DECLARE SECTION in C.
Only one level of qualification is allowed, that is, a host or indicator variable can be part of a structure, but that structure may not be nested within another structure.
Host and indicator variables must be one of the C data types shown in the following table.
Note: C does not support VARCHAR as in other languages where the length is specified in a 2-byte binary field in front of the actual value. Instead, C supports VARCHAR as a null-terminated string. This is true for input and output host variables in C. Null-terminated strings can also be used with CHAR columns in C.

C Data Types Compared to SQL Data Types

C Data Type	Example	SQL Data Type
single char	char x;	CHAR
char array	char x[10]	VARCHAR
char structure containing exactly one short variable followed by exactly one char array.	char struct { short len1; char text[9]; } hv1;	VARCHAR
decimal(precision, scale)	decimal(5,0)	DECIMAL
short or short int	short hv1;	SMALLINT
int or long int	int hv1;	INTEGER
float	float hv1;	FLOAT
double	double hv1;	FLOAT
char array	char dateHv[11];	DATE
char array	char timeHv[9];	TIME
char array	char timeStampHv[23];	TIMESTAMP

Comments on C Data Types

char array

The C char array is treated as a null-terminated string.

char hv1[10] is equivalent to VARCHAR(9).

The VARCHAR length is set based on the number of bytes preceding the null-terminating byte.

Char arrays for DATE, TIME, and TIMESTAMP also need the null-terminating byte.

char structure

The char array for the text is not null terminated.

decimal

Use of decimal requires #include decimal.h (provided by the IBM C Compiler), and the compiler option must not be ANSI. Precision and scale is optional. To print decimal values, use (with printf):

 %D(precision,scale)

host structures

In DATACOM mode, a host variable structure may be used. The host structure must be a C structure containing only valid host variables. The host structure must not be nested within another structure.

indicator variables

In DATACOM mode, a host indicator structure or array may be used. The structure or array must only contain short C variables. The indicator structure must not be nested within another structure.

INCLUDEs

INCLUDEs in the C language are basically the same as in PL/I except note the following:

The SQLCA is always automatically generated, so no INCLUDE should be used for it. However, you must code your own SQLDA and SQLVAR when using dynamic SQL.
The EXEC SQL INCLUDE <member name>; SQL statement can be used to include members from the PDS data set INCLUDE in z/OS (for z/VSE, the name in the EXEC SQL INCLUDE is the name of a member in a z/VSE library). INCLUDEs in C cannot be nested.
Because the Precompiler executes before the C Preprocessor, statements such as #include, #define, and typedef are not expanded. Unless the user executes the language preprocessor only before the CA Datacom/SQL C Preprocessor, host variables in #include files cannot be referenced, and #define and typedefs cannot be used to declare a host variable data type.