sql 怎么查询一个列的最大值

sql 怎么查询一个列的最大值

方法一

SELECt ID ,
Name ,
( SELECT MAX(LastUpdateDate)
FROM ( VALUES ( UpdateByApp1Date), ( UpdateByApp2Date),
( UpdateByApp3Date) ) AS UpdateDate ( LastUpdateDate )
) AS LastUpdateDate
FROM ##TestTable

方法二

SELECt ID ,
[Name] ,
MAX(UpdateDate) AS LastUpdateDate
FROM ##TestTable UNPIVOT ( UpdateDate FOR DateVal IN ( UpdateByApp1Date,
UpdateByApp2Date,
UpdateByApp3Date ) ) AS u
GROUP BY ID ,
Name

方法三

SELECT ID ,
name ,
( SELECT MAX(UpdateDate) AS LastUpdateDate
FROM ( SELECt tt.UpdateByApp1Date AS UpdateDate
UNIOn
SELECT tt.UpdateByApp2Date
UNIOn
SELECT tt.UpdateByApp3Date
) ud
) LastUpdateDate
FROM ##TestTable tt

select a.id from table a left outer join ( select name, max(num) max_num from table group by name ) b on a.name = b.name and a.num = b.max_num