SQL查询使用order子句从两个单独的表中进行选择

Question

我有两个表：

tickets
ticket_updates

我正在尝试运行一个查询，其中它显示票证表中的数据，并在ticket_updates表中order by最新datetime时间ticket_updates

SELECT * from tickets where status = 'Completed' order by ??? DESC LIMIT 0,50 

ticketnumber在tickets表匹配ticketnumber在ticket_updates表

Answer 1

SELECT t.*
FROM tickets AS t
JOIN ticket_updates AS tu ON t.ticketnumber = tu.ticketnumber
WHERE status = 'Completed'
ORDER BY tu.datetime DESC LIMIT 50

尝试这个。

Answer 2

一种方法是汇总ticket_updates表以获得所需的内容：

select t.*
from tickets t join
     (select ticketid, max(datetime) as max_datetime
      from ticket_updates
      group by ticketid
     ) tu
     on t.ticketid = tu.max_datetime
order by tu.max_datetime desc
limit 0, 50;

Answer 3

连接两个表，然后按以下顺序排序：

SELECT a.*
from tickets a, ticket_updates b
where a.ticketnumber = b.ticketnumber and
a.status = 'Completed'
order by b.YOUR_DATETIME_FIELD DESC LIMIT 0,50