Question

我需要一个SQL（SQL Server），根据当前的sg获取最早的日期。下面是当前sg为4-3的示例表（当前，因为结束日期是1900-01-01）。我想得到每位员工实际开始的日期（2015-01-01）。我真的需要一些帮助。

empno      position             sg           date_from         date_to
4508       ADMIN AIDE IV        4-3          2017-01-01        1900-01-01
4508       ADMIN AIDE IV        4-3          2016-01-01        2016-12-31
4508       ADMIN AIDE IV        4-3          2015-01-01        2015-12-31
4508       ADMIN AIDE IV        4-2          2014-01-01        2014-12-31
4508       ADMIN AIDE IV        4-2          2013-01-01        2013-12-31
1207       AIRCRAFT MECHANIC I  6-1          1988-01-01        1989-06-30
1207       AIRCRAFT MECHANIC II 8-7          2006-05-08        2015-12-31
1207       AIRCRAFT MECHANIC II 8-8          2016-01-01        1900-01-01
0889       DATA ENTRY OPERATOR  1-1          2000-12-12        2001-06-30
0889       ADMIN ASSISTANT VI   12-5         2017-03-10        1900-01-01
0889       ADMIN ASSISTANT VI   12-5         2016-01-01        2016-12-31

Answer 1

如果我理解正确，你可以用内部查询

来做到这一点

select  min(date_from)
from    yourTable
where   sg = (
            select  sg
            from    yourTable
            where   date_to = '1900-01-01'
        )

或加入

select  min(t1.date_from)
from    yourTable t1
join    yourTable t2
on      t1.sg = t2.sg
where   t2.date_to = '1900-01-01'

修改

要获得每个职位的最短日期，最简单的方法是将第二个查询调整为：

select t1.position, min(t1.date_from) from yourTable t1 join yourTable t2 on t1.sg = t2.sg and t1.position = t2.position where t2.date_to = '1900-01-01' group by t1.position

修改2

由于要求是获取empno列中每个值的最小日期，您需要做的是

select t1.empno, min(t1.date_from) from yourTable t1 join yourTable t2 on t1.sg = t2.sg and t1.empno = t2.empno where t2.date_to = '1900-01-01' group by t1.empno

您可以在工作中看到它here

Answer 2

如果sg不能有多个位置，您可以使用下一个查询

SELECT t.position, t.sg, MIN(date_from) AS date_from
FROM @t AS t
    INNER JOIN 
      (select sg from @t where date_to = '19000101') as cur
    ON t.sg = cur.sg
GROUP BY t.position, t.sg

Answer 3

解决方案：

SELECT TOP 1 *
FROM YourTableNameHere
ORDER BY Sg DESC, Date_From

更多详情：

将ORDER BY与TOP 1结合使用。下面我使用了一个可以在NEW QUERY窗口中运行的临时表。

试试这个：

CREATE TABLE #TempTable(
 Position varchar(20),
 Sg varchar(3),
 Date_From datetime,
 Date_To datetime)

INSERT INTO #TempTable (Position, Sg, Date_From, Date_To) 

SELECT 
        'ADMIN AIDE IV', '4-3', '2017-01-01', '1900-01-01'
UNION
SELECT 
        'ADMIN AIDE IV', '4-3', '2016-01-01', '2016-12-31'
UNION
SELECT 
        'ADMIN AIDE IV', '4-3', '2015-01-01', '2015-12-31'
UNION
SELECT 
        'ADMIN AIDE IV', '4-2', '2014-01-01', '2014-12-31'
UNION
SELECT 
        'ADMIN AIDE IV', '4-2', '2013-01-01', '2013-12-31'


SELECT TOP 1 *
FROM #TempTable
ORDER BY Sg DESC, Date_From

Answer 4

请使用以下查询：

    DECLARE @t TABLE 
    (ID INT IDENTITY (1,1),position VARCHAR(20), sg VARCHAR(10),date_from DATE,date_to DATE)

    INSERT INTO @t 
    VALUES
    ('ADMIN AIDE IV','4-3','2017-01-01','1900-01-01'),
    ('ADMIN AIDE IV','4-3','2016-01-01','2016-12-31'),
    ('ADMIN AIDE IV','4-3','2015-01-01','2015-12-31'),
    ('ADMIN AIDE IV','4-2','2014-01-01','2014-12-31'),
    ('ADMIN AIDE IV','4-2','2013-01-01','2013-12-31')

    SELECT  
        MIN(t1.date_from) AS [Earliest Date]
    FROM    
        @t t1 INNER JOIN @t t2 ON t1.sg = t2.sg
    WHERE   
        t2.date_to ='1900-01-01'

如何根据当前sg

4 个答案: