Using the VALUE Clause After a DESCRIBE

After you describe a SELECT, EXECUTE FUNCTION (or EXECUTE PROCEDURE), INSERT, or UPDATE statement, the characteristics of each column or expression in the select list of the SELECT statement, the characteristics of the values returned by the EXECUTE FUNCTION (or EXECUTE PROCEDURE) statement, or the characteristics of each column in an INSERT or UPDATE statement are returned to the system-descriptor area. Each value in the system-descriptor area describes the characteristics of one returned column or expression.

The following example uses GET DESCRIPTOR to obtain data type information from the demodesc system-descriptor area:

EXEC SQL get descriptor 'demodesc' value :index
       :type = TYPE,
       :len = LENGTH,
       :name = NAME;
printf("Column %d: type = %d, len = %d, name = %s\n",
      index, type, len, name);

The value that the database server returns into the TYPE field is a defined integer. To evaluate the data type that is returned, test for a specific integer value. For additional information about integer data type values, see Setting the TYPE or ITYPE Field.

In X/Open mode, the X/Open code is returned to the TYPE field. You cannot mix the two modes because errors can result. For example, if a particular data type is not defined under X/Open mode but is defined for HCL® OneDB® products, executing a GET DESCRIPTOR statement can result in an error.

In X/Open mode, a warning message appears if ILENGTH, IDATA, or ITYPE is used. It indicates that these fields are not standard X/Open fields for a system-descriptor area.

If the TYPE of a fetched value is DECIMAL or MONEY, the database server returns the precision and scale information for a column into the PRECISION and SCALE fields after a DESCRIBE statement is executed. If the TYPE is not DECIMAL or MONEY, the SCALE and PRECISION fields are undefined.