indexing keys AND related columns or just keys to increase speed in mysql

So if I have an sql query like these:

SELECT title, document FROM docs WHERE id = "1" and type = "2"

SELECT title FROM docs WHERE id = "1" 

SELECT title FROM docs WHERE member = "foo"

to maximize speed for the first one i. would I have to index only the keys (id and type together? seperate?) ii. would I also have to index title an开发者_如何学编程d document (together,separate)

same type of questions apply for the second one, and for the third query i. would I have to index only member? IM just trying to understand mysql retrieval and indexing.

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You need 2 indexes

(id, type, title)
(member, title)

• id, type makes id redundant
• adding title makes the index covering

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1) Index both id and type together, but not title and document

2) Index id only

3) index member only

in other word you have to index {id}, {id, type}, {member}