Saturday, January 15, 2011

How to eliminate Product Joins in a Teradata SQL query?

How to eliminate Product Joins in a Teradata SQL query?
Answers:

1. Ensure statistics are collected on join columns and this is especially important if the columns you are joining on are not unique.
2. Make sure you are referencing the correct alias.
3. Also, if you have an alias, you must always reference it instead of a fully qualified tablename.
4. Sometimes product joins happen for a good reason. Joining a small table (100 rows) to a large table (1 million rows) a product join does make sense.

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