You can use the DESCRIBE statement (or the PREPARE statement with the INTO option) to enter the column name, data type, and other data into the appropriate fields of the SQLDA structure.
Before the statement is executed, the SQLN and SQLDABC fields should be initialised as described above.
After the statement has been executed, the SQLD field will contain the number of parameters in the prepared statement. A SQLVAR record is set up for each of the parameters with the SQLTYPE and SQLLEN fields completed.
If you do not know how big the value of SQLN should be, you can issue a DESCRIBE statement with SQLN set to 1 and SQLD set to 0. No column detail information is moved into the SQLDA structure, but the number of columns in the results set is inserted into SQLD.