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

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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

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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

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

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