Allocates space for each variable described in each descriptor of sqlda, and assigns the address of this memory to the sqldata field of the corresponding descriptor.
struct sqlda * fill_sqlda( struct sqlda * sqlda );
sqlda if successful and returns NULL if there is not enough memory available.
Enough space is allocated for the database type and length indicated in the descriptor.
The SQLDA should be freed using the free_filled_sqlda function.