mysql optimization / how to use index tip...?

if this is my USERS table

user_id 
user_fname  
user_lname  
user_email  
user_pass   
user_verified   
user_city   
user_joined 
us开发者_运维问答er_lastlogin  
user_about

i set user_id as PRIMARY (is an auto incremental value)

thaen, should i set user_email as INDEX? other suggestion?

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You should add indexes to columns that are often used in query conditions, ordering, joining. There is no point in adding an index to a column that doesn't play any role in the query.

If you have thoughts about optimizing a query, at first, you should check it out in EXPLAIN query to see how complex the query is.

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You should use indexes when your table is searched more frequently than it gets updated. If your table is searched using user_email very often, then you may use indexes on that column.

Remember, if user_email field gets updated more often than being used in a search condition, then it will ultimately lead to a performance overhead.

Go here for further insight.