帮助sql join

Question

我有两张桌子：

表1： ID，PersonCode，名称，

表2： ID，Table1ID，位置，ServiceDate

我有一个查询将表1连接到table1.ID = table2.Table1ID，其中PersonCode ='XYZ'

我想要做的是返回Table1.PersonCode，Table1.Name，Table2.Location，Table2.ServiceDate，我不想要所有行，在表2中我只对最近ServiceDate的行感兴趣对于每个位置。我该怎么做呢？

Answer 1

这样的事情：

SELECT
    Table1.PersonCode, Table1.Name, Table2.Location, MAX(Table2.ServiceDate)
FROM
    Table1 
    INNER JOIN Table2 on Table1.ID = Table2.Table1ID 
WHERE
    TABLE1.PersonCode = 'XYZ'
GROUP BY
    Table1.PersonCode,Table1.Name, Table2.Location

Answer 2

使用MAX（ServiceDate）

Answer 3

尝试：

select Table1.PersonCode,Table1.Name, Table2.Location, Table2.ServiceDate
from Table1
join Table2 on table1.ID = table2.Table1ID 
where table1.PersonCode = 'XYZ'
and table2.ServiceDate = (select max(t2.ServiceDate)
                          from   table2 t2
                          where  t2.table1ID = table2.table1ID
                          and    t2.location = table2.location
                         );

Answer 4

我会使用INNER JOIN并选择第一条记录，根据Table2.ServiceDate以反向时间顺序排序记录。

SELECT TOP 1
    Table1.PersonCode, Table1.Name, Table2.Location, Table2.ServiceDate
FROM
    Table1 
    INNER JOIN Table2 on Table1.ID = Table2.Table1ID 
WHERE
    TABLE1.PersonCode = 'XYZ'
ORDER BY Table2.ServiceDate DESC
GROUP BY
    Table1.PersonCode,Table1.Name, Table2.Location