如何在基於SQL CASE語句的WHERE條件中過濾記錄

Question

我有以下case語句用於加載代碼表。我必須要找到的記錄數裝入碼表 與TRAN_CODE = 7時[GLI-SRC =「8」

INSERT INTO codes 
    SELECT CASE 
      WHEN [cash-amt] > 0 THEN '1' 
      WHEN [prod-n] = '42' 
        AND [tran-code] IN ('-1', '-2', '-3') THEN '17' 
      WHEN [gli-src] = '8' THEN '7' 
      WHEN [prod-n] = '42' 
        AND [gli-src] = 'L' 
        AND [tran-code] IN ('1', '2', '3') THEN '7' 
      WHEN [gli-src] = 'L' 
        AND [prod-n] = '60' 
        AND [tran-code] IN ('4', '5', '6') THEN '7' 
      ELSE '4' 
      END AS TRAN_CODE 
    FROM txn 

這是我曾嘗試雖然我很困惑如何過濾掉其他情況。

select COUNT(1) from txn 
where [CASH-AMT] <= 0 
and 
. 
. 
. 
. ???? 
and [gli-src] = '8' 

Answer 1

SELECT COUNT(1) 
FROM ( SELECT CASE 
       WHEN [cash-amt] > 0 THEN '1' 
       WHEN [prod-n] = '42' 
         AND [tran-code] IN ('-1', '-2', '-3') THEN '17' 
       WHEN [gli-src] = '8' THEN '7' 
       WHEN [prod-n] = '42' 
         AND [gli-src] = 'L' 
         AND [tran-code] IN ('1', '2', '3') THEN '7' 
       WHEN [gli-src] = 'L' 
         AND [prod-n] = '60' 
         AND [tran-code] IN ('4', '5', '6') THEN '7' 
       ELSE '4' 
       END AS TRAN_CODE, 
       [CASH-AMT], 
       [gli-src] 
     FROM txn) AS T 
WHERE [CASH-AMT] <= 0 
AND [gli-src] = '8' 
AND TRAN_CODE = 7