在SQL中的案例表達式

Question

我有一個簡單的案例表達式，運行在SQL服務器下面。我期待看到結果有超過12個HRS，超過25個HRS，超過45個HRS，等等。但是，我的結果只會返回超過12個HRS，少於12個HRS。請有人賜教我。

謝謝， 喬

SELECT 
STORE, 
CASE 
WHEN HOURS >12 THEN 'Over 12 HRS' 
WHEN HOURS >25 THEN 'Over 25 HRS' 
WHEN HOURS >45 THEN 'Over 45 HRS' 
WHEN HOURS >55 THEN 'Over 55 HRS' 
WHEN HOURS >75 THEN 'Over 75 HRS' 
WHEN HOURS >94 THEN 'Over 94 HRS' 
ELSE    'Less 12 HRS' 
END    AS HOURS, 
COUNT (ID)   AS PRD 

FROM 
(
    SELECT 
    ID, 
    STORE, 
    HOURS 
    FROM TABLE A 
)X 
GROUP BY STORE, 
CASE 
WHEN HOURS >12 THEN 'Over 12 HRS' 
WHEN HOURS >25 THEN 'Over 25 HRS' 
WHEN HOURS >45 THEN 'Over 45 HRS' 
WHEN HOURS >55 THEN 'Over 55 HRS' 
WHEN HOURS >75 THEN 'Over 75 HRS' 
WHEN HOURS >94 THEN 'Over 94 HRS' 
ELSE    'Less 12 HRS' 
END 

Answer 1

這是因爲你下令在錯誤的道路的情況：當HOURS >94是真實的，也HOURS >12必須是真實的，所以HOURS >94一定要來HOURS >12之前。

一般來說，條件必須從較強到較弱，而不是相反。

重新排序列表中的相反的方式將解決此問題：

CASE 
WHEN HOURS >94 THEN 'Over 94 HRS' 
WHEN HOURS >75 THEN 'Over 75 HRS' 
WHEN HOURS >55 THEN 'Over 55 HRS' 
WHEN HOURS >45 THEN 'Over 45 HRS' 
WHEN HOURS >25 THEN 'Over 25 HRS' 
WHEN HOURS >12 THEN 'Over 12 HRS' 
ELSE    'Less 12 HRS' 
END AS HOURS 

Answer 2

在第一個匹配行的case停止，所以13小時滿足所述第一條件，象23小時，和75小時，並等。

您需要反轉邏輯。一個簡單的方法是顛倒比較順序：

(CASE WHEN HOURS <= 12 THEN 'Less 12 HRS' 
     WHEN HOURS <= 25 THEN 'Over 12 HRS' 
     WHEN HOURS <= 45 THEN 'Over 25 HRS' 
     WHEN HOURS <= 55 THEN 'Over 45 HRS' 
     WHEN HOURS <= 75 THEN 'Over 55 HRS' 
     WHEN HOURS <= 94 THEN 'Over 75 HRS' 
     ELSE 'Over 94 HRS' 
END) AS HOURS, 

我還建議您重命名組。喜歡的東西：

(CASE WHEN HOURS <= 12 THEN '00-12 HRS' 
     WHEN HOURS <= 25 THEN '12-25 HRS' 
     WHEN HOURS <= 45 THEN '25-45 HRS' 
     WHEN HOURS <= 55 THEN '45-55 HRS' 
     WHEN HOURS <= 75 THEN '55-75 HRS' 
     WHEN HOURS <= 94 THEN '75-94 HRS' 
     ELSE '94+ HRS' 
END) AS HOURS, 

Answer 3

25，45，55，75，和94均大於12，所以這第一條件檢查的比賽，而且也沒有必要進一步評估所有。你想這樣寫：

CASE 
    WHEN HOURS >94 THEN 'Over 94 HRS' 
    WHEN HOURS >75 THEN 'Over 75 HRS' 
    WHEN HOURS >55 THEN 'Over 55 HRS' 
    WHEN HOURS >45 THEN 'Over 45 HRS' 
    WHEN HOURS >25 THEN 'Over 25 HRS' 
    WHEN HOURS >12 THEN 'Over 12 HRS' 
ELSE     'Less 12 HRS' 
END