Sql isnull函數 不起作用

ISNULL函數起作用的前提是 該條數據存在

可以先通過 IF EXISTS 來判斷是否存在

IF EXISTS (
    SELECT 
     ISNULL( CASE  WHEN  (SELECT COUNT(1) FROM beau_User where  UserId=mpo.superior_user_id and PID='10539300278' )>0 THEN
  (ISNULL(mpo.buy_commission, 0)+ISNULL(mpo.superior_commission, 0))/1000   ELSE

(ISNULL(mpo.buy_commission, 0)+ISNULL(mpo.head_commission, 0))/1000 END,0) p

from mm_pdd_order  mpo where mpo.head_user_id='59686498966192128' and 
 create_time >='2020-02-01' and (order_status !=-1 and order_status !=4 and order_status !=8 and order_status !=10) 
)
BEGIN
        SELECT 
             ISNULL( CASE  WHEN  (SELECT COUNT(1) FROM beau_User where  UserId=mpo.superior_user_id and PID='10539300278' )>0 THEN
        (ISNULL(mpo.buy_commission, 0)+ISNULL(mpo.superior_commission, 0))/1000   ELSE

    (ISNULL(mpo.buy_commission, 0)+ISNULL(mpo.head_commission, 0))/1000 END,0) p

    from mm_pdd_order  mpo where mpo.head_user_id='59686498966192128' and 
     create_time >='2020-02-01' and (order_status !=-1 and order_status !=4 and order_status !=8 and order_status !=10) 
END
ELSE 
    BEGIN
        --如果不存在
        SELECT
            0  p
        END