SELECT + JOIN query

[nicdp]

I have to tables:
1) USERS with all emails and ids
2) USER_RELATIONS with the relations that tell me in which category the user is.

1 USER can be in MORE THEN 1 CATEGORY.

I made this select statement to take all users subscribed to cat 4 OR 7, but I get some users 2 times... I want to get the users who are subscribed to both cats only 1 time.

WHAT'S WRONG?

SELECT users.email FROM users LEFT JOIN users_relations ON users.id = users_relations.user_id WHERE 1=1 AND (users_relations.id_cat=4 OR users_relations.id_cat=7);

[Lars_Berg]

SELECT distinct users.email 
FROM users inner JOIN users_relations 
ON users.id = users_relations.user_id 
WHERE  users_relations.id_cat in (1,4)