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 and 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.