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Message Posted: Thu, 27 Mar 2003 @ 15:29:07 GMT

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Subj:   Re: On Derived Table
From:   Ford, Richard W

However, note that the use of each type of table has its pro's and con's -

A derived table is only good for as long as the query is active, once the query has reached a commit (or rollback) point the table is gone. A derived table cannot be optimized (i.e. you cannot assign any kind of index or collect stats on it).

A Global Temp table is something that you can set up and lives in the Teradata catalog, and because you control the DDL of it you can set up indexes and collect stats on whatever columns you wish - thus you can optimize it based on your query needs. When you need to use the table, you reference by name and data can be inserted/updated/deleted from it. This table is good for the duration of your Teradata session - once you log out of Teradata, the table is emptied of its data and is ready for your next Teradata session.


Rick Ford

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