SQL查詢使用order子句從兩個單獨的表中進行選擇

Question

我有兩個表：

tickets
ticket_updates

我正在嘗試運行一個查詢，其中它顯示票證表中的數據，並在ticket_updates表中order by最新datetime時間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

嘗試這個。

Answer 2

一種方法是匯總ticket_updates表以獲得所需的內容：

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

連接兩個表，然后按以下順序排序：

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