High performance MySQL Note-The 5th chapter indexing the role of the Performance-003 index

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1). Indexes reduce the amount of data the server has to examine.
2). Indexes Help the server avoid sorting and temporary tables.
3). Indexes turn random I/O into sequential I/O.

Lahdenmaki and Leach ' s book also introduces a Three-star system for grading how suitable an index was for a query. The index earns one star if it places relevant rows adjacent to all other, a second star if it rows is sorted In the order of the query needs, anda final star if it contains all the columns needed for the query.

High performance MySQL Note-The 5th chapter indexing the role of the Performance-003 index