如何获取所有类似条目 MySQL 的 maxdate

Question

我问了这个问题并得到了 mysql 的一个很好的答案：How to assign date value to all returned mysql queries 但现在我需要在 MS SQL (SQL Server 2005) 中做同样的事情。需要注意的是，我有一个案例陈述似乎正在破坏事情。我有两个这样的查询：

select * from (select row_number()
  over (order by a.device ASC)
  AS rownum, a.device, staff, requestDate, m.maxDate, attribute = 
                 REPLACE((SELECT attribute AS [data()]
                 FROM deviceList
                 WHERE device = a.device
                 ORDER BY device FOR xml PATH('')), ' ',  ' ')
  FROM deviceList a
  INNER JOIN (SELECT device, MAX(requestDate) AS maxDate
                 FROM ASSIGNMENT GROUP BY device) m on m.device = a.device
  RIGHT JOIN Assignment
      ON (Assignment.device=a.device)
  GROUP BY a.device, staff, maxDate, requestDate, contract)
  AS B WHERE B.rownum > 0;





select * from (select row_number()
  over (order by a.device ASC)
  AS rownum, a.device, staff, requestDate, CONVERT(
    varchar, dateadd(year,
    (CASE
        WHEN contract = '10' THEN 1
        WHEN contract = '20' THEN 2
        WHEN contract = '30' THEN 3
        ELSE 3
        END), m.maxDate) 107) as myEndDate, attribute = 
                 REPLACE((SELECT attribute AS [data()]
                 FROM deviceList
                 WHERE device = a.device
                 ORDER BY device FOR xml PATH('')), ' ',  ' ')
  FROM deviceList a
  INNER JOIN (SELECT device, MAX(requestDate) AS maxDate
                 FROM ASSIGNMENT GROUP BY device) m on m.device = a.device
  RIGHT JOIN Assignment
      ON (Assignment.device=a.device)
  GROUP BY a.device, staff, myEndDate, requestDate, contract)
  AS B WHERE B.rownum > 0;                 

第一个语句效果很好，就像条目（具有相同“设备”标签的条目）具有正确的 endDate。但是，当我尝试根据案例陈述增加日期时，事情就会出错。日期增加但不相同。为什么case语句会破坏这种性质的东西？

更新： 如果我对一台设备有两个日期值：

2/1/2010
1/1/2010

合约 = 10

查询后的日期分别为：

2/1/2011
2/1/2012

Answer 1

您必须在GROUP BY 子句中使用整个CASE 语句。 SQL Server 不一定会在执行GROUP BY 之前处理SELECT 元素，因此无法使用在那里定义的别名。 (Longer explanation here)。

SELECT * FROM (SELECT ROW_NUMBER()
  OVER (ORDER BY a.device ASC)
  AS rownum, a.device, staff, requestDate, CONVERT(
    varchar, dateadd(year,
    (CASE
        WHEN contract = '10' THEN 1
        WHEN contract = '20' THEN 2
        WHEN contract = '30' THEN 3
        ELSE 3
        END), m.maxDate) 107) as myEndDate, attribute = 
                 REPLACE((SELECT attribute AS [data()]
                 FROM deviceList
                 WHERE device = a.device
                 ORDER BY device FOR xml PATH('')), ' ',  ' ')
  FROM deviceList a
  INNER JOIN (SELECT device, MAX(requestDate) AS maxDate
                 FROM ASSIGNMENT GROUP BY device) m on m.device = a.device
  RIGHT JOIN Assignment
      ON (Assignment.device=a.device)
  GROUP BY a.device, staff, CONVERT(
    varchar, dateadd(year,
    (CASE
        WHEN contract = '10' THEN 1
        WHEN contract = '20' THEN 2
        WHEN contract = '30' THEN 3
        ELSE 3
        END), m.maxDate) 107), requestDate, contract)
  AS B WHERE B.rownum > 0;