'Table access' diaporamas de présentation

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?? 1. ? / ?? ??? ???? ??? ??. ????? TAB_A : TAB_A_X1 : YY + MM + DD + SALE_NO QUERY. SELECT A.YY || A.MM, DEPT, SUM(SALE_QTY) FROM TAB_A A WHERE A.YY || A.MM BETWEEN '9410' AND '9504' GROUP BY A.YY || A.MM, DEPT ;. ??? QUERY. SELECT A.YY || A.MM, DEPT, SUM(SALE_QTY)

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Presentation Outline

Presentation Outline. SQL Writing Process SQL Standards Using Indexes The Optimizer FROM, WHERE Clauses EXPLAIN SQL Trace Sub-Selects and Joins Tips and Tricks. Caveat. Although many of these principles apply to all databases, Oracle will be used in the examples.

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Index Internals

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Oracle Optimizer

Oracle Optimizer. Types of Optimizers. There are different modes for the optimizer RULE: Rule-based optimizer (RBO) Deprecated; not updated since 1994 CHOOSE: Default option. Chooses cost-based optimizer (CBO) if statistics available, rule-based optimizer otherwise.

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Basic Optimization

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Are Your Statistics Bad Enough?

Are Your Statistics Bad Enough?. Verify the effectiveness of gathering optimizer statistics Jaromir D.B. Nemec UKOUG 2005. 27.10.2005. Gathering Statistics. The way from ANALYZE TABLE to DBMS_STATS Increasing number of parameters and options changing defaults CBO more intelligent

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Oracle Index study for Event TAG DB

Oracle Index study for Event TAG DB. M. Boschini matteo.boschini@mib.infn.it S. Della Torre stefano.dellatorre@mib.infn.it. Outline. TAG DB issue: space usage issue INDEX accounting for ~ 50% of used space... query performance Tests with random data Tests with AMS01 data

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Optimizing Join Statements

Optimizing Join Statements. To choose an execution plan for a join statement, the optimizer must choose: Access Paths Join Operation Join Order These Choices are related. Lets examine the different possible join operations. The outer table or the driving table. The inner Table.

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