在SQL Server上优化SQL查询

Question

我在SQL Server上有一个需要优化的SQL查询。 运行它大约需要16分钟。

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

我想出了以下内容，但似乎没有抓住CountOfActiveSKUs = 0的记录。

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

任何帮助表示赞赏，谢谢！

Answer 1

我可以这样写：

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;

除非绝对必要，否则我将不SELECT DISTINCT 。 如有必要，请使用显式的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

不要过滤状态，请使用条件SUM计算status ='A'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

[1]首先，我将这样重写原始查询：

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]然后我将创建以下索引

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

注意＃1：将IIF（expr，T，F）（SQL2012 +）替换为CASE

注意＃2：检查重复/相似的索引（在dbo.SKU表上）

注意＃3：索引还应包括“状态”列。

Answer 4

尝试这个

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