如何在sql中使用union？答案

【问题标题】：How to use union in sql?如何在sql中使用union？
【发布时间】：2013-12-14 16:22:33
【问题描述】：

我在 sql 数据库 [dbo].[ClockInClockOut] 中有一个包含 3 列的表：[UserId]、ClockInClockOutTypeId]、[CreatedDate]。我需要显示像

这样的数据

UserName  CreatedDate      TimeIn      TimeOut

abc      12/31/2013        13:19:51    13:22:37
xyz      1/31/2013         14:19:51    15:19:51

我在 sql 中这样做：

select u.[UserName],
          CONVERT(VARCHAR(20), c.[CreatedDate], 101) as [Date],
          CASE WHEN c.[ClockInClockOutTypeId]=1 and  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]

我得到了这个结果：

   UserName  CreatedDate      TimeIn       TimeOut

    abc      12/31/2013        13:19:51    null
    abc      12/31/2013           null     14:19:51

在第 1 行第 3 列时间可以，但我需要在第 4 列而不是在第 4 列的第 2 行超时。

【问题讨论】：

您有一个名为ClockInClockOut 的表，位于一个身份不明的数据库中（名称无关紧要）。让你的术语直截了当；如果您将表称为数据库，您将混淆您自己和您尝试寻求帮助的每个人。

标签： sql join union

【解决方案1】：

您需要在第二次加入ClockInClockOut，而不是union the results。

我会做类似的事情

SELECT 
  u.UserName,
  CONVERT(VARCHAR(20), c1.[CreatedDate], 101) as [Date],
  CONVERT(VARCHAR(20), c1.[CreatedDate], 108) as InTime,
  CONVERT(VARCHAR(20), c2.[CreatedDate], 108) as OutTime
FROM [ClockInClockOut] as c1
INNER JOIN [ClockInClockOut] as c2 ON c1.UserId = c2.UserId 
           -- getting the specific date is a little tricky, unquestionably better ways exist
           AND CONVERT(VARCHAR(20), c1.[CreatedDate], 101) = CONVERT(VARCHAR(20), c2.[CreatedDate], 101)
INNER JOIN [UserProfile] as u on c1.UserId = u.[UserId] 
WHERE
  c1.ClockInClockOutTypeId = 1 AND c2.ClockInClockOutTypeId = 2

或者，如果您不喜欢，您可以汇总您的初始查询...

SELECT
  a.UserName, a.Date
  MAX(a.InTime) As InTime,
  MAX(a.OutTime) As OutTime
FROM (
  SELECT 
      u.[UserName],
      CONVERT(VARCHAR(20), c.[CreatedDate], 101) as [Date],
      CASE WHEN c.[ClockInClockOutTypeId]=1 and  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] 
) a
GROUP BY a.UserName, a.Date

【讨论】：

【解决方案2】：

在ClockInClockOut 表上使用自联接可能比尝试 UNION 更容易。

SELECT u.UserName, i.Date, i.InTime, o.OutTime
  FROM (SELECT u.UserName,
               CONVERT(VARCHAR(20), c.CreatedDate, 101) AS Date,
               CONVERT(VARCHAR(20), c.CreatedDate, 108) AS InTime
          FROM ClockInClockOut AS c 
        WHERE c.ClockInClockOutTypeId = 1) AS i
  JOIN (SELECT u.UserName,
               CONVERT(VARCHAR(20), c.CreatedDate, 101) AS Date,
               CONVERT(VARCHAR(20), c.CreatedDate, 108) AS InTime
          FROM ClockInClockOut AS c 
         WHERE c.ClockInClockOutTypeId = 2) AS o
    ON i.UserName = o.UserName AND i.Date = o.Date
  JOIN UserProfile AS u ON i.UserId = u.UserId

如果您需要处理在某一天多次签到的人，或者在午夜之前签到并在午夜之后结帐的人等，您可能需要使联接条件更加复杂。但是对于简单的白班一次in，一旦出局，这将起作用。

【讨论】：

【解决方案3】：

测试数据

DECLARE @ClockInClockOut TABLE 
([UserId] INT, [ClockInClockOutTypeId] SMALLINT, [CreatedDate] DATETIME)

INSERT INTO @ClockInClockOut
VALUES 
(1,1,'2013-12-10 09:42:08.603'),
(1,2,'2013-12-10 16:42:08.603'),
(1,1,'2013-12-11 16:42:08.603'),
(1,2,'2013-12-11 18:42:08.603'),
(2,1,'2013-12-12 09:42:08.603'),
(2,2,'2013-12-12 16:42:08.603'),
(2,1,'2013-12-13 11:42:08.603'),
(2,2,'2013-12-13 15:42:08.603')

DECLARE @UserProfile TABLE (USERID INT, USERNAME VARCHAR(20))
INSERT INTO @UserProfile
VALUES (1, 'Mark'),
       (2, 'John')

查询

 ;With TimeI
 AS
   (
   SELECT UserID, [CreatedDate], 
               CONVERT(VARCHAR(20), [CreatedDate], 108)  AS InTime
   FROM @ClockInClockOut
   WHERE [ClockInClockOutTypeId]=1 
   ),
TimeO 
AS
  (
     SELECT UserID,[CreatedDate], 
              CONVERT(VARCHAR(20), [CreatedDate], 108)  AS OutTime
   FROM @ClockInClockOut
   WHERE [ClockInClockOutTypeId]=2
  )
SELECT DISTINCT USERNAME , CAST(CO.[CreatedDate] AS DATE) AS [CreatedDate], TI.Intime, T.OutTime
FROM @UserProfile UP INNER JOIN @ClockInClockOut CO
ON UP.USERID = CO.UserId
INNER JOIN TimeI TI
ON UP.USERID = ti.UserId 
AND CAST(CO.[CreatedDate] AS DATE) = CAST(TI.[CreatedDate] AS DATE) 
INNER JOIN TimeO T
ON UP.USERID = t.UserId 
AND CAST(CO.[CreatedDate] AS DATE) = CAST(T.[CreatedDate] AS DATE)

结果集

USERNAME    CreatedDate      Intime      OutTime
John          2013-12-12    09:42:08    16:42:08
John          2013-12-13    11:42:08    15:42:08
Mark          2013-12-10    09:42:08    16:42:08
Mark          2013-12-11    16:42:08    18:42:08

【讨论】：