如何在SQL中使用自我加入？

Question

I have 2 tables in sql

1. SELECT TOP 1000 [UserId]
      ,[UserName]
      ,[Password]
      ,[FirstName]
      ,[LastName]
      ,[Password_Expiry]
      ,[Modified]
      ,[ModifiedBy]
      ,[CreatedBy]
      ,[Type]
      ,[Privileges]
  FROM [Paramount].[dbo].[UserProfile]



2. SELECT TOP 1000 [Id]
      ,[UserId]
      ,[ClockInClockOutTypeId]
      ,[CreatedDate]
  FROM [Paramount].[dbo].[ClockInClockOut]

i need to retrieve data form both tables like-

[UserName]| Date [CreatedDate]|[CreatedDate](just time in) as TimeIn | [CreatedDate](just Time Out) as time out 
Mr.abc xyz| 4/12/13           | 1:30 Pm                              | 3:30Pm

i have tried this but not getting the required result:-

SELECT u.[username], 
       c.[clockinclockouttypeid], 
       c.[createddate] 
FROM   [Paramount].[dbo].[clockinclockout] AS c 
       JOIN [Paramount].[dbo].[userprofile] AS u 
         ON c.userid = u.[userid] 
WHERE  c.[clockinclockouttypeid] = 1 

SELECT u.[username], 
       c.[clockinclockouttypeid], 
       c.[createddate] 
FROM   [Paramount].[dbo].[clockinclockout] AS c 
       JOIN [Paramount].[dbo].[userprofile] AS u 
         ON c.userid = u.[userid] 
WHERE  c.[clockinclockouttypeid] = 2 rProfile] as u on c.UserId = u.[UserId] where c.[ClockInClockOutTypeId]=2

any help will be appreciated, thanks in advance!

Answer 1

Try UNION like this

select [UserName], MAX([Date]) as [Date], MAX(InTime) as InTime, MAX(OutTime) as OutTime
FROM (
    select u.[UserName],
           CONVERT(VARCHAR(20), c.[CreatedDate], 101) as [Date],
           CONVERT(VARCHAR(20), c.[CreatedDate], 108) as InTime,
           null as OutTime
    from [ClockInClockOut] as c 
    inner join [UserProfile] as u on c.UserId = u.[UserId] 
    where c.[ClockInClockOutTypeId]=1 

    UNION 
    select u.[UserName],
           CONVERT(VARCHAR(20), c.[CreatedDate], 101)  as [Date],
           null as InTime,
           CONVERT(VARCHAR(20), c.[CreatedDate], 108)as OutTime
    from [ClockInClockOut] as c 
    inner join [UserProfile] as u on c.UserId = u.[UserId] 
    where c.[ClockInClockOutTypeId]=2
) tt
GROUP BY [UserName]

SQL Demo 1

Update :

You can also use CASE WHEN like below :

select [UserName], MAX([Date]) as [Date], MAX(InTime) as InTime, MAX(OutTime) as OutTime
FROM
(
   select u.[UserName],
          CONVERT(VARCHAR(20), c.[CreatedDate], 101) as [Date],
          CASE WHEN c.[ClockInClockOutTypeId]=1 THEN CONVERT(VARCHAR(20), c.[CreatedDate], 108) ELSE null END as InTime,
          CASE WHEN c.[ClockInClockOutTypeId]=2 THEN CONVERT(VARCHAR(20), c.[CreatedDate], 108) ELSE null END as OutTime
   from [ClockInClockOut] as c 
   inner join [UserProfile] as u on c.UserId = u.[UserId] 
) tt
GROUP BY [UserName]

SQL Demo 2

Answer 2

An SQL join clause - corresponding to a join operation in relational algebra - combines columns from one or more tables in a relational database . We know about inner join , left join , natural join etc in SQL . But most of them don't know what is self join and how does it work ? Now we are going to know what is self join and how does it work . We can use a self join when a table references data in itself. To clearly understand see the following table .

See , This is our Employee table and we have to find out who works under the manager . Here Sonam is the manager and Rahul and Jay works under Sonam . Thereafter The manager of Sonam is Kunal . Furthermore The manager of Ram is Rani and Rani does'nt have any manager . That mean you can say She is CEO. Hope you will understand. So let's learn how to write this query . See the final report of their works under manager. read full article from here What is self join in SQL . read full article from here Self join in sql