mysql合併欄位用concat，將多個數據合併為一個欄位用group_concat，切記group_concat要與group by連用，這樣資料就不會只剩下一條。。。

例子：

                select
a.*, concat(
c.provencie,
c.city,
c.district,
c.location
) addressStr,
group_concat(u.userName order by u.id) rusername
from automat a
LEFT JOIN auto_addr b ON (a.id = b.aut_id)
LEFT JOIN address c ON (b.addrId = c.id)
LEFT JOIN replenishment_allocation r ON (a.id = r.autoId)
LEFT JOIN user u ON (u.id = r.userId)

group by a.id;

連線了數個表，group_concat預設連線符號是逗號，也可以使用引數修改，並且，裡面可以用order by排序，簡直不能再好用，記下來~