How to insert data only if data doesn't already exist in MYSQL?

This is what I'm doing right now:

Execute a query and check if the date to be inserted already exists in a table.

If date doesn't exist:

Another query wil开发者_如何学Gol insert the date into the table.

How can these two query be combined?

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IF NOT EXISTS (SELECT * FROM X WHERE A=B)
    INSERT INTO ...

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Taken from here:

INSERT IGNORE INTO Table (EmailAddr) VALUES ('test@test.com')

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you can put the two statements together into a stored procedure