JOIN 걸어 UPDATE

UPDATE Table1

SET a = B.a

, b = @b

, c = @c
, d   = @d

FROM Table1 A
JOIN (
    SELECT
        PSNL_NO
     , DDC_PAYM_YM
     , DEPT_CD
     , PAYM_TARG_AMT
     FROM  Table1      WHERE DDC_PAYM_YM = @DDC_PAYM_DT 
) B ON A.a = B.a AND A.b = B.b AND A.c = B.c
WHERE A.a = @DDC_PAYM_DT
AND A.b =@b