在SQL Server上優化SQL查詢

Question

我在SQL Server上有一個需要優化的SQL查詢。 運行它需要將近16分鐘。

SELECT DISTINCT DeptNo, 
       BrandDesc, 
       MfgDesc, 
       CountOfActiveSKUs = 
        COALESCE((SELECT COUNT(*) 
           FROM dbo.SKU k 
           WHERE k.Status = 'A' 
           AND k.BrandDesc = s.BrandDesc 
           AND k.MfgDesc = s.MfgDesc 
           AND k.DeptNo = s.DeptNo), 
          0) 
      FROM dbo.SKU s 
     ORDER BY BrandDesc 

我想出了以下內容，但它似乎並不抓住它有CountOfActiveSKUs = 0

SELECT DISTINCT DeptNo, 
       BrandDesc, 
       MfgDesc, 
       CountOfActiveSKUs = COALESCE(Count(*), 0) 
      FROM dbo.SKU 
      WHERE Status = 'A' 
     GROUP BY BrandDesc, MfgDesc, DeptNo 
     ORDER BY BrandDesc 

任何幫助表示讚賞記錄， 謝謝！

Answer 1

我會寫爲：

SELECT DeptNo, BrandDesc, MfgDesc, 
     SUM(CASE WHEN status = 'A' THEN 1 ELSE 0 END) OVER (PARTITION BY BrandDesc, MfgDesc, DeptNo) as CountOfActiveSKUs 
FROM dbo.SKU s 
ORDER BY BrandDesc; 

我將離開SELECT DISTINCT出來，除非它是絕對必要的。如果有必要，則使用一個明確的GROUP BY：

SELECT DeptNo, BrandDesc, MfgDesc, 
     SUM(CASE WHEN status = 'A' THEN 1 ELSE 0 END) as CountOfActiveSKUs 
FROM dbo.SKU s 
GROUP BY DeptNo, BrandDesc, MfgDesc 
ORDER BY BrandDesc; 

Answer 2

不要過濾狀態，用狀態=「A」使用條件的總和計數的SKU。

SELECT DISTINCT DeptNo, 
       BrandDesc, 
       MfgDesc, 
       SUM(CASE WHEN status = 'A' THEN 1 ELSE 0 END) as CountOfActiveSKUs 
      FROM dbo.SKU 
     GROUP BY BrandDesc, MfgDesc, DeptNo 
     ORDER BY BrandDesc 

Answer 3

嘗試此

SELECT s.DeptNo, s.BrandDesc, s.MfgDesc, count(k.Status) as CountOfActiveSKUs 
FROM dbo.SKU s LEFT OUTER JOIN 
dbo.SKU k ON 
k.Status = 'A' AND k.BrandDesc = s.BrandDesc 
AND k.MfgDesc = s.MfgDesc AND k.DeptNo = s.DeptNo 
GROUP BY s.DeptNo, s.BrandDesc, s.MfgDesc 
ORDER BY BrandDesc 

Answer 4

[1]首先，我會重新寫從而原始查詢：

SELECT DeptNo, BrandDesc,MfgDesc, SUM(IIF(s.Status = 'A', 0, 1)) AS Count_StatusA 
FROM dbo.SKU AS s 
GROUP BY s.DeptNo, s.BrandDesc, s.MfgDesc 
-- ORDER BY s.BrandDesc -- Uncomment this line only when necessary 

和

[2]然後，我會創建以下索引

CREATE /*UNIQUE*/ /*[NON]CLUSTERED*/ INDEX IUN_SKU_BrandDesc_DeptNo_MfgDesc 
ON dbo.SKU (BrandDesc, DeptNo, MfgDesc, Status) 

說明＃1：IIF（表達式，T，F）（SQL2012 +）可以與CASE代替WHEN EXPR則T ELSE六最終

注2：檢查是否有重複/相似指數（上dbo.SKU表）

注意＃3：索引還應該包括de Status列。