How to use Boolean logic in a mySQL SELECT query

How can I check if email = '$e' or username = '$e' inside my MySQL query.

Here is my MySQL query so far.

"SELECT user_id FROM users WHERE (email = '$e' AND pass=SHA1('$p'))"  开发者_如何转开发      

If you want to modify you existing query so that it works even if $e matches username, you can do:

SELECT user_id 
FROM users 
WHERE (email = '$e' OR username = '$e') AND pass=SHA1('$p')