获取客户通话的总费用

Question

我有 2 个表 = 客户及其通话记录

现在我想根据通话时长以及特定月份（比如 2015 年 1 月）向他们收费。

这是计算通话费用的标准 -

A) 对于来电，收费为每秒 1 个单位。 Example if the duration is 250 seconds then cost is 250

B) 对于拨出电话，for the first 2mins, the cost is fixed at 500 units。随后几秒钟的费用为2 units per second。

例如，如果传出持续时间为 5 分钟，则费用为 500 units + 2*3*60 units = 860 units

下表是：

customer table with columns id, name, phone

history table with columns id, incoming_phone, outgoing_phone, duration, dialed_on (YYYY-MM-DD)

我针对我的情况提出了以下查询：

来电费用：

select c.name, c.phone, h.duration as cost
from customer c join history h on c.phone = h.incoming_phone

当我运行上述查询时，我没有收到任何语法错误。

拨出电话费用：

select c.name, c.phone, CASE
    WHEN h.duration > 120 THEN 500 + 2*(h.duration-120)
    ELSE 2*(h.duration-120)
END; as cost
from customer c join history h on c.phone = h.outgoing_phone

当我运行上述查询时，我得到了syntax error like "ERROR 1109 (42S02) at line 1: Unknown table 'c' in field list"

我想加入这两个查询并获取总费用并将字段显示为姓名、电话、费用

我仍然需要为特定月份添加一个条件来限制 2015 年 1 月的数据，但我被这个方法卡住了。

Answer 1

错误是由于END 后面的分号; 造成的。

听起来您的最终查询是这样的：

SELECT c.name, 
       c.phone, 
       SUM(CASE WHEN h.direction = 'in' THEN h.duration END) as IncomingCost,
       SUM(CASE WHEN h.direction = 'out' AND h.duration > 120 THEN 500 + 2*(h.duration-120)
                WHEN h.direction = 'out' AND h.duration <= 120 THEN 500
       END) as OutgoingCost,
       SUM(CASE WHEN h.direction = 'in' THEN h.duration END +
       CASE WHEN h.direction = 'out' AND h.duration > 120 THEN 500 + 2*(h.duration-120)
            WHEN h.direction = 'out' AND h.duration <= 120 THEN 500
       END) as TotalCost
FROM customer c 
JOIN (SELECT 'out' as directon, duration, dialed_on, outgoing_phone as phone 
      FROM history 
      WHERE YEAR(dialed_on) = 1995
      AND MONTH(dialed_on) = 1
      UNION ALL
      SELECT 'in' as direction, duration, dialed_on, incoming_phone as phone
      FROM history
      WHERE YEAR(dialed_on) = 1995
      AND MONTH(dialed_on) = 1
     ) h ON c.phone = h.phone
GROUP BY c.name,
         c.phone