Indexing on composite key

Question

If I have a table and I create a index on Emp.Id, Emp.Name and Emp.Surname .(3 fields out of 10). Now if I query table with just Emp.Id will it fetch query based upon indexing (fast) or normal?

Got solution at https://stackoverflow.com/questions/15349110/index-on-composite-attributes — Divanshu Aggarwal, Nov 27 '19 at 17:40

score 1 · Answer 1 · answered Nov 27 '19 at 17:42

1

Think of a telephone book.

It's indexed on last_name first, then first_name.

Does this help you look up a person by their last name only? Yes.

Does it help you look up a person by their first name only? No.

answered Nov 27 '19 at 17:42

Bill Karwin

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score 0 · Answer 2 · answered Nov 27 '19 at 17:40

0

If id is the first column in the index, then it can be used for a query filtering on the id.

This is a common practice when creating indexes, putting commonly used columns first, but then including others.

answered Nov 27 '19 at 17:40

Gordon Linoff

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Indexing on composite key

2 Answers2