Question

我有2个表client_headquarter＆amp;客户端

client_headquarter： ID

客户端： id，headquarterid，clentname，tscreated

我想显示所有总部，并且每个总部都会显示“最近的”客户端（ts_created），如果它存在，则显示其中的空白。我希望所有这些都按照没有客户端，老客户端和底层最新客户端的总部进行排序。

有人可以协助查询吗？

Answer 1

SELECT client_headquarter.id, max(clients.tscreated)
FROM client_headquarter 
LEFT OUTER JOIN clients ON clients.headquarterid = client_headquarter.id
GROUP BY client_headquarter.id
ORDER BY MAX(clients.tscreated) ASC

Answer 2

像...这样的东西。

> select chq.id, count(clientname), max(tscreated) from clients c
> left outer join client_headquarter chq on c.hearquarterid = chq.id
> group by chq.id
> order by count(clientname) DESC, max(tscreated) DESC

Answer 3

select 
    ch.id as [Headquarter ID],
    c.clientname as [Most Recent Client Name],
    c.tscreated as [Date Created]
from 
    client_headquarter ch
    left join 
    (select 
        headquarterid,
        max(tscreated)
    from
        clients
    group by
        headquarterid
    ) recent on recent.headquarterid = ch.id
    left join clients c on c.headquarterid = ch.headquarterid and c.tscreated = recent.tscreated
order by
    c.tscreated

如果多个客户具有相同的创建日期，这将为单个总部创建多个行。如果这是不可取的，那么必须定义和实施一些区分胜利者的明确方法。

如何从左外连接中检索最大日期？

3 个答案: