select decode('ABC',null,10,'AB',100,'ABC',100) RESULT from dual
SELECT T_YGJBXX.YGID,FJ,MAX(CASE WHEN (DRDWBH IS NOT NULL) THEN DRDWBH ELSE '1070000000' END) AS DRDWBH FROM T_JSX,T_YGJBXX WHERE (T_JSX.DRDWBH<>T_YGJBXX.SZDWBH OR T_JSX.DRDWBH IS NULL) AND T_YGJBXX.YGID=T_JSX.YGID .... GROUP BY T_YGJBXX.YGID,FJ
AS DRDWBH FROM T_JSX,T_YGJBXX
WHERE (T_JSX.DRDWBH<>T_YGJBXX.SZDWBH OR T_JSX.DRDWBH IS NULL)
AND T_YGJBXX.YGID=T_JSX.YGID
....
GROUP BY T_YGJBXX.YGID,FJ