Question about using or in mysql query

I wanted to get some clarification, if using OR in a sql statement on indexes does it use the index or no?

For example if I have this query:

SELECT * FROM account_orders WHERE accountid = 1 OR accountid = 0

I have an index on the accountid field

Will mysql use the index? Or would it 开发者_StackOverflow社区be better to use a union? I keep reading that mysql doesnt use an index with an or statement, or perhaps Im reading that incorrectly. Any help/explanation would be helpful. Using mysql 5.x

Database won't use an index if you use OR like you have.

The work around is to rephrase it using IN. as follows:

SELECT * FROM account_orders WHERE accountid IN (1, 0)

Databases will use an index (if available) with this syntax

Best to prefix your select statement with EXPLAIN. This will report about the result of the query and if any indices were used.

EXPLAIN SELECT * FROM account_orders WHERE accountid = 1 OR accountid = 0

This is somewhat off topic, but you could just do:

SELECT * FROM account_orders WHERE accountid IN (0,1)