describe output (SQLDA)

Obtains row format information about the result set of a prepared dynamic SQL statement and stores that information in a SQLDA structure.

exec sql describe [output] statement_name 
 using descriptor sqlda_name;

output: An optional keyword that has no effect on the describe output statement but provides conformance to the SQL standard.

statement_name: The name (specified in a prepare statement) that represents the select statement to be executed.

sqlda_name: The name of a SQLDA structure that will store the information returned by the describe output statement.

...

exec sql open curs2 using descriptor input_descriptor;

exec sql describe output statement using descriptor

     output_descriptor;

output_descriptor->sqlda_column->sqlda_sqldata = character;

output_descriptor->sqlda_column->sqlda_datafmt.datatype =     CS_CHAR_TYPE;

output_descriptor->sqlda_column->sqlda_datafmt.maxlength = 20;

output_descriptor->sqlda_column->sqlda_sqllen = 20;

output_descriptor->sqlda_column->sqlda_datafmt.format =

     (CS_FMT_NULLTERM | CS_FMT_PADBLANK);

exec sql fetch curs2 into descriptor output_descriptor;

The information obtained is the data held in the SQLDA fields, such as the type, name, length (or precision and scale, if a number), nullable status, and number of items in the result set.
The information is about the result columns from the select column list.