15.10 - Example: Creating a Procedure that Consumes a Queue Table - Teradata Database

Teradata Database SQL Data Definition Language Syntax and Examples

Teradata Database
December 2015
Programming Reference

The following procedure consumes a shopping cart queue table row that returns the three variables sp_ordernum, sp_product, and sp_quantity:

    CREATE PROCEDURE consumecart(OUT sp_ordernum CHARACTER(15), 
                        OUT sp_product  CHARACTER(30), 
                                 OUT sp_quantity INTEGER) 
    SELECT AND CONSUME TOP 1 ordernum, product, quantity INTO 
     :sp_ordernum, :sp_product, :sp_quantity FROM shoppingcart;

The system retrieves the queue table row at the top of the FIFO queue from a single AMP and deletes it from the shoppingcart table.

The row was consumed first because it had been in the queue for the longest duration as determined by its QITS value being the oldest of all rows in the queue. The system builds the response row as specified in the expression list and returns it to the requestor in variables.