SQL最快的'GROUP BY'脚本

Question

我编辑GROUP BY命令的方式有什么不同吗？

我的代码:

SELECT Number, Id 
    FROM Table
    WHERE(....)
    GROUP BY Id, Number

如果我像这样编辑它会更快:

 SELECT Number, Id 
    FROM Table
    WHERE(....)
    GROUP BY Number , Id

Answer 1

这个例子是平等的。

数据定义语言：

CREATE TABLE dbo.[WorkOut]
(
    [WorkOutID] [bigint] IDENTITY(1,1) NOT NULL PRIMARY KEY,
    [TimeSheetDate] [datetime] NOT NULL,
    [DateOut] [datetime] NOT NULL,
    [EmployeeID] [int] NOT NULL,
    [IsMainWorkPlace] [bit] NOT NULL,
    [DepartmentUID] [uniqueidentifier] NOT NULL,
    [WorkPlaceUID] [uniqueidentifier] NULL,
    [TeamUID] [uniqueidentifier] NULL,
    [WorkShiftCD] [nvarchar](10) NULL,
    [WorkHours] [real] NULL,
    [AbsenceCode] [varchar](25) NULL,
    [PaymentType] [char](2) NULL,
    [CategoryID] [int] NULL
)

询问：

SELECT wo.WorkOutID, wo.TimeSheetDate 
FROM dbo.WorkOut wo
GROUP BY wo.WorkOutID, wo.TimeSheetDate

SELECT DISTINCT wo.WorkOutID, wo.TimeSheetDate 
FROM dbo.WorkOut wo

SELECT wo.DateOut, wo.EmployeeID
FROM dbo.WorkOut wo
GROUP BY wo.DateOut, wo.EmployeeID

SELECT DISTINCT wo.DateOut, wo.EmployeeID 
FROM dbo.WorkOut wo

执行计划：