sqlserver-中表的自链接

USE [luck]
GO

/****** Object:  Table [dbo].[User_Activity]    Script Date: 2017/8/20 15:14:32 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[User_Activity](
    [ID] [int] NOT NULL,
    [Actity] [nchar](100) NULL,
    [UserId] [int] NULL,
 CONSTRAINT [PK_User_Activity] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SELECT [ID]
      ,[Actity]
      ,[UserId]
  FROM [luck].[dbo].[User_Activity]
  
  where [Actity]=‘打球‘ and  [Actity]=‘约炮‘

SELECT UserId
FROM [luck].[dbo].[User_Activity]
where [Actity]=‘打球‘ 
and  UserId in
(
  SELECT UserId
  FROM [luck].[dbo].[User_Activity]
  where [Actity]=‘约炮‘
 )

SELECT M.UserId FROM(
SELECT UserId
FROM [luck].[dbo].[User_Activity]
where [Actity]=‘打球‘ ) M,
(
SELECT UserId
FROM [luck].[dbo].[User_Activity]
where [Actity]=‘约炮‘) N

WHERE M.UserId=N.UserId

SELECT M.UserId FROM [User_Activity] M,
                     [User_Activity] N

WHERE M.[Actity]=‘打球‘ AND N.[Actity]=‘约炮‘ AND
      M.UserId=N.UserId