使用計數優化SQL查詢

Question

我使用ASP.NET成員資格，最重要的是我添加了一些與用戶有一對多關係的表。

一個用戶有很多筆，筆記本等

我編碼一個自定義的成員提供和已經修改了選擇查詢檢索所有關於用戶以及用戶具有筆的數量和信息「工具」的總數，但查詢顯然是災難性的。 無論如何得到這些信息？ 這是我曾嘗試：

SET STATISTICS TIME ON 
SELECT m.Email, m.PasswordQuestion, m.IsApproved, m.CreateDate, m.LastLoginDate, 
     u.LastActivityDate, m.LastPasswordChangedDate, u.UserId, m.IsLockedOut, 
     m.LastLockoutDate, CAST(m.Comment as nvarchar(max)) as Comment, 
     COUNT(DISTINCT cl.Id) AS NumberOfPens, 
     COUNT(DISTINCT cf.Id)+ 
      COUNT(DISTINCT cm.Id) + 
      COUNT(DISTINCT ce.Id) + 
      COUNT(DISTINCT cl.Id) + 
      COUNT(DISTINCT cp.Id) + 
      COUNT(DISTINCT csl.Id)+ 
      COUNT(DISTINCT cs.Id) + 
      COUNT(DISTINCT cshl.Id) AS NumberOfTools 
FROM aspnet_Membership AS m 
     INNER JOIN aspnet_Users AS u ON m.UserId = u.UserId 
     INNER JOIN Pens AS cf ON u.UserId = cf.Owner 
     INNER JOIN Notebooks AS cm ON u.UserId = cm.Owner 
     INNER JOIN Rulers AS ce ON u.UserId = ce.Owner 
     INNER JOIN Calculators AS cl ON u.UserId = cl.Owner 
     CROSS JOIN aspnet_Applications AS a 
GROUP BY u.UserId, m.Email, m.PasswordQuestion, m.IsApproved, 
     m.CreateDate, m.LastLoginDate, u.LastActivityDate, 
     m.LastPasswordChangedDate, m.IsLockedOut, m.LastLockoutDate, 
     CAST(m.Comment as nvarchar(max)) 

SET STATISTICS TIME OFF 

9分鐘11秒91級的用戶！

Answer 1

作爲一個快速打擊，最終拿出cross join - 你沒有使用它，它只是增加你的結果並放慢速度。

此外，你可以做接合前的計數，這將節省group by並允許RDBMS並行查詢，像這樣：

SELECT  
    m.Email, 
    m.PasswordQuestion, 
    m.IsApproved, 
    m.CreateDate, 
    m.LastLoginDate, 
    u.LastActivityDate, 
    m.LastPasswordChangedDate, 
    u.UserId, 
    m.IsLockedOut, 
    m.LastLockoutDate, 
    CAST(m.Comment as nvarchar(max)) as Comment, 
    PenCount AS NumberOfPens, 
    PenCount + NotebookCount + RulerCount + CalculatorCount AS NumberOfTools 
FROM 
    aspnet_Membership AS m 
    INNER JOIN aspnet_Users AS u ON 
     m.UserId = u.UserId 
    INNER JOIN (select owner, count(1) as PenCount from Pens group by owner) AS cf ON 
     u.UserId = cf.Owner 
    INNER JOIN (select owner, count(1) as NotebookCount from Notebooks group by owner) AS cm ON 
     u.UserId = cm.Owner 
    INNER JOIN (select owner, count(1) as RulerCount from Rulers group by owner) AS ce ON 
     u.UserId = ce.Owner 
    INNER JOIN (select owner, count(1) as CalculatorCount from Calculators group by owner) AS cl ON 
     u.UserId = cl.Owner 

需要注意的是，如果一個用戶可能沒有所有工具，你會想要做LEFT連接代替inner連接，然後將所有*Count列與coalesce(Count, 0)包裝在一起。

Answer 2

SELECT m.Email, m.PasswordQuestion, m.IsApproved, m.CreateDate, m.LastLoginDate, 
     u.LastActivityDate, m.LastPasswordChangedDate, u.UserId, m.IsLockedOut, 
     m.LastLockoutDate, CAST(m.Comment as nvarchar(max)) as Comment, 
     penCount, 
     notebookCount + rulerCount + calculatorCount AS toolCount 
FROM aspnet_Membership m 
JOIN aspnet_Users u 
ON  u.userId = m.userId 
CROSS APPLY 
     (
     SELECT COUNT(*) 
     FROM pens 
     WHERE owner = u.UserId 
     ) p (penCount) 
CROSS APPLY 
     (
     SELECT COUNT(*) 
     FROM notebooks 
     WHERE owner = u.UserId 
     ) n (notebookCount) 
CROSS APPLY 
     (
     SELECT COUNT(*) 
     FROM rulers 
     WHERE owner = u.UserId 
     ) r (rulerCount) 
CROSS APPLY 
     (
     SELECT COUNT(*) 
     FROM calculators 
     WHERE owner = u.UserId 
     ) c (calculatorCount)