Oracle Query Performance Tuning 110 - Single Column index and Composite index explained
This is a continuation from previous session which covered what an index is, how the index improves a query, and measure the query improvement.
In this session, we will dive into a more technical discussion and create single column index and composite index. Column statistics will be used to explain why the query optimizer will choose index on column A over index on column B, what is the difference between index created using columns (A,B) and index created using columns (B,A).
--gather runtime query statistics
ALTER SESSION SET STATISTICS_LEVEL='ALL';
--view execution plan of previously executed query
SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(null,null,'ALLSTATS LAST +peeked_binds +cost +bytes'));
This video is a continuation from my previous video.
Link to my previous video.
• Oracle Query Performance Tuning 109 -...
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