17.10 - Example: Creating a Procedure that Consumes a Queue Table - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Syntax and Examples

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1144-171K
Language
English (United States)

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) 
    BEGIN 
    SELECT AND CONSUME TOP 1 ordernum, product, quantity INTO 
     :sp_ordernum, :sp_product, :sp_quantity FROM shoppingcart;
    END;

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.