Need Your help with query_read

[madzat]

Hey there, plz i need your help with sql so here my problem i have field7 and i made page for Normal user and super user so all super user is group 13 to read the group im using

PHP Code:

$db->query_read("SELECT username FROM ". TABLE_PREFIX ."user WHERE usergroupid = 13"); 


and is working well so my problem now i want to make page for super user using the field7 when i try read

PHP Code:

$db->query_read("SELECT username, field7 FROM ". TABLE_PREFIX ."user LEFT JOIN mo_userfield ON(mo_user.userid=mo_userfield.userid)"); 


i get all member list so i want just group 13 if add

PHP Code:

$db->query_read("SELECT username, field7 FROM ". TABLE_PREFIX ."user LEFT JOIN mo_userfield ON(mo_user.userid=mo_userfield.userid && usergroupid=13)"); 


is not working any help plz

Thx