SQL语句关于树查询

.菜单树查询
SELECT
    A.*
FROM
    MENU A
WHERE
    A.ID IN (31, 51)
UNION
    SELECT
        C.*
    FROM
        MENU C
    WHERE
        C.ID IN (
            SELECT
                B.PARENTID
            FROM
                MENU B
            WHERE
                B.ID IN (31, 51) and B.PARENTID!=0
        )

2.MYSQL分页

SELECT
U.UUID,
U.USERACCOUNT,
U. PASSWORD,
U.IDENTITY,
U.AREA,
U.ROLE_UUID ROLEUUID,
U.CREATETIME,
R.ROLENAME
FROM
USERS U
LEFT JOIN ROLE R ON U.ROLE_UUID=R.UUID
WHERE
1 = 1
LIMIT ?, ?