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Message Posted: Mon, 16 Jun 2003 @ 13:33:52 GMT

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EXPLAIN is a simple text description of the steps that Teradata will take to process your query. This is built into the database itself and is therefore very fast. It may not be easy to visualize exactly what is going on however. (such as which steps will be performed in parallel.)

VISUAL EXPLAIN is a separate application. It is much slower than EXPLAIN because it has to build a set of tables (in a QCD database) to produce its output. It allows you to easily visualize such things as parallel steps however, and adds a lot of additional functionality. (such as displaying the definitions of the tables/views used in the query.)

To use Visual Explain you must first purchase and install the product. (Available as part of the TTU 7.0 package) When you first launch it you must use the Tools, Control Center menu to create the QCD database that you will be using. (It will ask you to select a data source [a DBS] and then to logon) After you have logged on click on the SetupQCD button to create the required database. (You will have to enter a database name, owner/parent database, and the amount of space you want to allocate to this new database.) You are now ready to run a visual explain. Use the Tools, Launch QCF menu to do this. Enter the query you want to explain in the large text box, and press Submit. (You may also want to check Delete after use if you dont need this query to remain in the QCD database.)

The above is a very brief overview of basic functionality. you should read the Users Guide or Help file for a better understanding of all the functionality available to you.

Mike Dempsey
Teradata Client Tools

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