与日期和 ID 进行比较？

Question

使用 SQL Server 2000

我想根据 Table1.personid 获取 Table2.TimeIn Table2.TimeOut 以及如果 Table1.Date = Table3.Date 那么它应该需要一个 Table3.TimeIn, Table3.TimeOut。

3 个表格

表1

ID    Date  

001 20090503 
001 20090504 
001 20090506 
002 20090505 
002 20090506 

等等……，

表2

ID    TimeIn TimeOut

001 08:00:00 18:00:00
002 08:00:00 21:00:00

等等……，

表3

ID    Date  TimeIn TimeOut

001 20090504 10:00:00 22:00:00
001 20090505 17:00:00 23:00:00
002 20090505 12:00:00 21:00:00 

等等……，

Select Table1.ID, 
       Table1.Date, 
       Table2.TimeIn, 
       Table2.TimeOut 
  from Table1 
Inner Join Table2 on Table1.ID = Table2.ID 

如果 Table1.Date = Table3.Date 那么它应该采取 Table3.TimeIn, Table3.TimeOut 否则 Table2.TimeIn, Table2.Timeout

预期输出

ID Date TimeIn TimeOut

001 20090503 08:00:00 18:00:00
001 20090504 10:00:00 22:00:00 
001 20090506 08:00:00 18:00:00
002 20090505 12:00:00 21:00:00
002 20090506 08:00:00 21:00:00

等等……，

如何为这种情况编写查询？

Answer 1

员工时间表后备？：

SELECT Table1.ID
    ,Table1.Date
    ,COALESCE(Table3.TimeIn, Table2.TimeIn) AS TimeIn
    ,COALESCE(Table3.TimeOut, Table2.TimeOut) AS TimeOut
FROM Table1
INNER JOIN Table2 -- Always have an expected schedule for an employee
    ON Table1.ID = Table2.ID
LEFT JOIN Table3 -- May.may not have an actual schedule for an employee
    ON Table3.ID = Table1.ID
    AND Table3.Date = Table1.Date
/*
ORDER BY Table1.ID
    ,Table1.Date
*/