회원가입을 수정해서 프로그램을 만드는 중인데...

SELECT mb_recommend order_person, mb_23 in_date, mb_21 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_26 in_date, mb_24 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_29 in_date, mb_27 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_32 in_date, mb_30 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_35 in_date, mb_33 amt
FROM `g4_member`

이렇게 하면 먹히는데

===========================



SELECT mb_recommend order_person, mb_23 in_date, mb_21 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_26 in_date, mb_24 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_29 in_date, mb_27 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_32 in_date, mb_30 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_35 in_date, mb_33 amt
FROM `g4_member`
) a





select a.* from (
SELECT mb_recommend order_person, mb_23 in_date, mb_21 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_26 in_date, mb_24 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_29 in_date, mb_27 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_32 in_date, mb_30 amt
FROM `g4_member`
UNION ALL
SELECT mb_recommend order_person, mb_35 in_date, mb_33 amt
FROM `g4_member`
) a


이렇게 하면 오류가 남니다....

이유를 모르겠네요.

좀 알려주세요..........