这是有效的MySQL查询吗？

DELETE FROM users WHERE userId = \'$userId\'
DELETE FROM messages WHERE userId = \'$userId\'
DELETE FROM files WHERE userId = \'$userId\'
DELETE FROM notes WHERE userId = \'$userId\'

[CONSTRAINT [symbol]] FOREIGN KEY
    [index_name] (index_col_name, ...)
    REFERENCES tbl_name (index_col_name,...)
    [ON DELETE reference_option]
    [ON UPDATE reference_option]

DELETE  u, m, f, p
FROM    users u
LEFT JOIN
        messages m
ON      m.user_id = u.id
LEFT JOIN
        files f
ON      f.user_id = u.id
LEFT JOIN
        posts p
ON      p.user_id = u.id
WHERE   u.id = 1

users

id = 1

WHERE users.userid = \'$userId\'.