Secondary Index


A secondary index is an index that refers to a clustered index (SQL Server, MySQL/InnoDB) or Index-Organized Table (Oracle). In other words, an index on an index.

Accessing table data via a secondary index is slower than a similar query on a heap-table.

About the Author

Photo of Markus Winand
Markus Winand tunes developers for high SQL performance. He also published the book SQL Performance Explained and offers in-house training as well as remote coaching at http://winand.at/

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"Order by RAND()" - can use Index?

Feb 23 at 12:06 Markus Winand ♦♦ 936
random index mysql order-by-rand
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index for better performance for a merge operation

Feb 20 at 11:43 antilet 1
merge index
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Join with inequalities only

Dec 16 '14 at 12:06 Markus Winand ♦♦ 936
inequality join