DB2 SQL: The Order Of Clause Evaluation In A SELECT Statement

• DB2 SQL: The Order Of Clause Evaluation In A SELECT Statement

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  Carl Eric Johnson - click to view profile

  Description:

  Ever wonder how DB2 (or Oracle or SQL Server or MySQL, for that matter) parses and processes a SELECT statement? Which clause is evaluated first? Which one comes next? This show answers these questions and more, with useful tips that will serve you well when coding your own SELECT statements. Carl Eric Johnson discovered this by accident once, when he coded his first OUTER JOIN syntax and created a very long-running query. After getting into the mind of DB2, he made a simple tweak, and it complete in microseconds.