mysql - 如何在查询中仅乘以一行？

Question

SELECT user_id, currency, SUM( price ) AS totalPrice, created
FROM accounts WHERE user_id IN ( SELECT users.id FROM users
                                 WHERE country_id ='$con_id' )
AND created BETWEEN  '2013-02-01' AND  '2013-02-28' GROUP BY currency

这个查询给了我类似的结果

Curreny  totalPrice
SEK      10
USD      10

我只想从 7 乘以瑞典克朗。我在数据库中只有美元汇率，所以我想在查询中将它乘以7以获得瑞典克朗汇率。我怎样才能在这个查询中做到这一点？

Answer 1

你的问题有点令人困惑。如果我正确理解您的问题，您想将总价值乘以7货币是否等于SEK。

SELECT  user_id, 
        currency, 
        SUM(price) * IF(currency = 'SEK', 7, 1) totalPrice, 
        created
FROM    accounts
WHERE   user_id
        IN 
        (
            SELECT users.id
            FROM users
            WHERE country_id =  '$con_id'
        ) AND 
        created BETWEEN  '2013-02-01' AND  '2013-02-28'
GROUP   BY currency

Answer 2

我会将所有转换率存储在一个表中。对于 SEK，您存储 7.0 als 转换率和 vor USD 1.0。只需将总价格乘以转化率（带子查询）

Answer 3

这是一个丑陋的实现方式：

SELECT user_id, currency,
       CASE WHEN currency = 'SEK' THEN SUM(price)*7
       ELSE SUM(price) END totalPrice, created
FROM accounts
WHERE user_id
IN ( SELECT users.id FROM users
     WHERE country_id =  '$con_id')
AND created BETWEEN  '2013-02-01' AND  '2013-02-28'
GROUP BY currency