使用子查询选择其他记录

Question

我尝试列出第一个订单日期的所有客户记录

表客户

customer_id | customer_name
    1       +    John
    2       +    Brad

表格订单

order_id  | customer_id | date
   1      +      1      + 2013-10-12 01:00:00
   2      +      1      + 2013-11-18 09:00:00
   3      +      2      + 2013-11-21 02:00:00

的MySQL

$get_ch_raw = "select c.*, a.*, ch.* from `customers` c  left join `admin` a on 
a.admin_id=c.admin_id left join `call_history` ch on 
ch.customer_id=c.customers_id 
order by c.customers_id desc"

，结果应该是这样的：

1       +    John    +   2013-10-12 01:00:00
2       +    Brad    +   2013-11-21 02:00:00

在这种情况下，我不确定如何使用子查询选择第一个订单。

Answer 1

这应该这样做：

SELECT c.customer_id, c.customer_name, MIN(o.date) date FROM customers c
LEFT JOIN orders o USING (customer_id)
GROUP BY c.customer_id

小提琴here。