16.20 - product join - Query Scheduler

Teradata Query Scheduler User Guide

prodname
Query Scheduler
vrm_release
16.10
16.20
created_date
May 2017
category
User Guide
featnum
B035-2512-086K

In Teradata SQL, the type of join that occurs when the WHERE conditional of a SELECT statement causes the Teradata Database system to compare all qualifying rows from one table to all qualifying rows from another table. Because each row of one table is compared to each row of another table, this join can be costly in terms of system performance.

Product joins without an overall WHERE constraint are considered unconstrained (Cartesian). If the tables to be joined are small, the effect of an unconstrained join on performance may be negligible, but if they are large, there may be a severe negative effect on system performance.