if else條件使用sql查詢

Question

我有問題為下表生成SQL查詢。 這是我的表：

County          | Store     | Stock | Display | Designation
--------------- | --------- | ----- | ------- | ------------
USA             | USD       | 1     | Yes     | Merchandiser
USA             | USD       | 2     | Yes     | Promoter

我想成為這樣的結果

County          | Store     | Stock | Display | Designation
--------------- | --------- | ----- | ------- | ------------
USA             | USD       | 2     | Yes     | Merchandiser
USA             | USD       | 2     | Yes     | Promoter

方案是如果指定是促銷，則使用顯示和庫存數據。 如果Designation來自Merchandiser，請使用Promoter for Stock data中的數據如何實現這一目標？

Answer 1

Select a.Country, a.Store
, Stock = CASE WHEN a.Designation = "Merchendiser" THEN b.Stock ELSE a.Stock
, Display = CASE WHEN a.Designation = "Merchendiser" THEN b.Display ELSE a.Display
, a.Designation
FROM YourTable a LEFT JOIN YourTable b WHERE b.Designation = "Promoter"

可以做到這一點。 目前無法測試。

編輯：我看到你沒有說明你使用的SQL（即SQL服務器，MySQL，PostgreSQL等，所以取決於這個解決方案可能無法運行）。

Answer 2

嘗試這個

SELECT County, 
           Store , 
           (CASE WHEN (Designation = 'Merchandiser') THEN (SELECT SUM(STOCK) FROM TABLE WHERE County = County AND Designation = 'Promoter' GROUP BY County) ELSE STOCK END) AS "stock",
           Display, 
           Designation
FROM table

此請求為您提供所需的結果。

Answer 3

我想你期待像這樣的查詢

Select a.Country, a.Store
    , (CASE WHEN a.Designation = "Merchendiser" THEN (select  Top 1 b.Stock from YourTable b where b.Designation = "Promoter" and b.Country = a.Country and b.Store = a.Store order by id desc) ELSE a.Stock) as Stock
    , a.Display
    , a.Designation
    FROM YourTable a WHERE b.Designation = "Promoter"

Answer 4

請嘗試以下代碼來創建臨時表

--===== If the test table already exists, drop it
 IF OBJECT_ID('TestDB..#mytable','U') IS NOT NULL
     DROP TABLE #mytable
 --===== Create the test table with 
 CREATE TABLE #mytable 
        (
        Country varchar(20),
        Store varchar(20),
        Stock int,
        Display varchar(5),
        Designation varchar(20)
        )
   --===== Insert the test data into the test table
 INSERT INTO #mytable 
       (Country, Store, Stock, Display, Designation)


 SELECT 'SG','a','2','YES','Merchandiser' UNION ALL
 SELECT 'SG','a','4','YES','Promoter' 

現在使用以上查詢

SELECT Country, 
       Store , 
       (CASE WHEN (Designation = 'Merchandiser') THEN (SELECT SUM(STOCK) FROM #mytable WHERE Country = Country AND Designation = 'Promoter' GROUP BY Country) ELSE STOCK END) AS "stock",
       Display, 
       Designation FROM #mytable