Dynamic SQL prepared statement commands are the only command type that allows the application to query the server for the inputs required to execute the command and for the format of the command’s results:
A ct_dynamic describe-input command causes the server to send the number and format of parameters that are required to execute the statement. See “Step 2: Get a description of command inputs” for details.
A ct_dynamic describe-output command causes the server to send the number and formats of result columns that the statement returns. See “Step 3: Get a description of command outputs” for details.
