Using IN operator in MySQL you can match the value from a set of values or a subquery.
Example of MySQL IN:
SELECT * FROM user WHERE country IN ('IN','AUS');
Here both the user from IN and AUS will be shown in the result.
You can also check for exception like:
SELECT * FROM user WHERE country NOT IN ('IN','AUS');
Here all the user will be displayed except IN and AUS.
You can also use a subquery:
SELECT * FROM user WHERE state IN ( SELECT state_id from STATE WHERE country = 221 );