CODEWITHSUNDEEP
mysql
gordyr
gordyr

Reputation: 6276

Why is MySQL showing 'using where' in the 'extra' column?

I have a very simple query which really needs to be as fast as possible...

The query is:

select users.userid, users.firstname, users.lastname
       from users_table users   
       where userid IN(1,4,6)

userid set as the primary key...

EXPLAIN returns the following:

id  |select_type|table|type |possible_keys|key    |key_len|ref |rows|Extra
1   |SIMPLE     |users|range|PRIMARY      |PRIMARY|4      |NULL|3   |Using where

Now, I was under the impression that 'Using where' is a bad thing?

Can anybody explain why I might be seeing this?

Upvotes: 2

Views: 1181

Answers (2)

Ray
Ray

Reputation: 41428

In your query, the where is the only thing it can use. It looks like it's using a primary key due to the IN clause being direct comparison to an indexed field (in this case your pk) so it don't get much better than this! Actually, it's impossible to get better than this...

Upvotes: 2

AndreKR
AndreKR

Reputation: 33678

It's ok to have "Using where" in MySQL because of this issue. Check the keycolumn to see if the key is actually used.

Upvotes: 2

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