sql-server-2008 - 高效的 TSQL 查询

Question

有没有更有效的方法来编写这个 SQL 查询？

它在大约 45 秒内从一组 100,000 行中返回大约 800 行。

我正在使用 Sql Server 2008 R2

Select a.Div as Division
      ,a.Room as RoomLocation
      ,a.Form as Forms
      ,a.Nums as TotalNumberLocations
From AView a
Where a.Id = '1'
And a.Div = 'A'
Group By a.Div, a.Nums, a.Room, a.Form

union

Select b.Div as Division
      ,b.Room as RoomLocation
      ,b.Form as Forms
      ,b.Nums as TotalNumberLocations
From AView b
Where b.Id = '1'
And b.Div = 'G'
Group By b.Div, b.Nums, b.Room, b.Form

union

Select c.Div as Division
      ,c.Room as RoomLocation
      ,c.Form as Forms
      ,c.Nums as TotalNumberLocations
From AView c
Where c.Id = '1'
And c.Div = 'R'
Group By c.Div, c.Nums, c.Room, c.Form
Order By Forms asc, TotalNumberLocations asc

Answer 1

当您可以在 IN 子句中包含值时，为什么要使用 UNION？你正在扫描桌子三遍。

Select Div as Division
      ,Room as RoomLocation
      ,Form as Forms
      ,Nums as TotalNumberLocations
From AView 
Where Id = '1'
And Div IN ('A','G','R')
Group By Div, Nums, Room, Form
Order By Forms asc, TotalNumberLocations asc

Answer 2

与其他答案类似，但是您也可以GROUP BY将distinct

Select distinct Div as Division
      ,Room as RoomLocation
      ,Form as Forms
      ,Nums as TotalNumberLocations
From AView a
Where Id = '1'
And Div in ('A', 'G', 'R')
Order By Forms asc, TotalNumberLocations asc

Answer 3

我会假设列Id和Div表上的索引对AView这个查询的性能非常有益，可能比重写查询要多得多。