Passing parameters to external functions

Data types

The following SQL data types can be passed to an external library:

SQL data type	C type
CHAR	Character data, with a specified length
VARCHAR	Character data, with a specified length
BINARY	Binary data, with a specified length
TINYINT	1-byte integer
BIGINT	Signed 8-byte integer
INT	Unsigned 4-byte integer
SMALLINT	Unsigned 2-byte integer
UNSIGNED BIGINT	Unsigned 8-byte integer
VARBINARY	Binary data, with a specified length
REAL	Single precision floating point number
DOUBLE	Double precision floating point number

You cannot use date or time data types, and you cannot use exact numeric data types.

To provide values for INOUT or OUT parameters, use the set_value API function. To read IN and INOUT parameters, use the get_value API function.

Passing NULL

You can pass NULL as a valid value for all arguments. Functions in external libraries can supply NULL as a return type for any data type.

External function return types

The following table lists the supported return types, and how they map to the return type of the SQL function or procedure.

C data type	SQL data type
void	Used for external procedures.
char *	function returning CHAR().
long	function returning INTEGER
float	function returning FLOAT
double	function returning DOUBLE.

If a function in the external library returns NULL, and the SQL external function was declared to return CHAR(), then the return value of the SQL extended function is NULL.