SQL获取不同的ID，但日期最新

Question

您好，我想获得不同的 FireUPRN，但日期是最新的 (FRADate)。

问题：

我不断收到错误 -

*Msg 241, Level 16, State 1, Line 4
Conversion failed when converting datetime from character string.
Warning: Null value is eliminated by an aggregate or other SET operation.*

代码：

SELECT *

FROM TblFire 
inner join (
SELECT Max(FRADate) as FireDateID, 
FRADate 
FROM TblFire GROUP BY FRADate)
FireDateID
ON FireDateID.FireDateID = TblFire.FireUPRN

Answer 1

您的查询很混乱，取日期列的最大值并将其称为 id。如果没有表格布局，我认为这就是您真正想要的：

SELECT f.*
FROM TblFire f INNER JOIN
     (SELECT FireUPRN, MAX(FRADate) as FRADate
      FROM TblFire
      GROUP BY FireUPRN
     ) fmax
     ON f.FRADate = fmax.FRADate and f.FireUPRN and fmax.FireUPRN;

Answer 2

试试这个：（ID 是 TblFire 的主键）

SELECT * FROM TblFire  t1
JOIN 
(
   SELECT ID, MAX(FRADate) AS FRADate
   FROM TblFire
   WHERE FRADate is not null 
   GROUP BY FRADate
) t2
ON T1.FRADate = t2.FRADate
AND t1.ID = t2.ID

Answer 3

有时它比看起来更容易......

SELECT FireUPRN, Max(FRADate) as FRADate
FROM TblFire 
GROUP BY FireUPRN