Question

我编写了以下查询以返回有关在X时间内进行的购买的一些统计信息。但由于某种原因，每个“COUNT”列返回总行数。我是否错误地组织了查询？

SELECT COUNT(*) as countTotal, SUM(`cost`) as cost, COUNT(`paymentType` = 'credit') as count_credit, COUNT(`paymentType` = 'cash') as count_cash 
FROM `purchase` WHERE `date` >= '2011-5-4'

更新

我刚决定使用子查询。这就是我最终的目标。

SELECT 
COUNT(*) as countTotal,
SUM(`cost`) as cost, 
(SELECT COUNT(*) FROM `purchase` WHERE `paymentType` = 'credit') as count_credit, 
(SELECT COUNT(*) FROM `purchase` WHERE `paymentType` = 'cash') as count_cash 
FROM `purchase` WHERE `date` >= '2011-5-4'

UPDATE2

使用的ypercubes回答如下。

Answer 1

count确实返回查询的域或组的行数。看起来您需要按PaymentType进行分组才能实现您的目标。

SELECT PaymentType, COUNT(*) as countTotal, SUM(`cost`) as cost, 
FROM `purchase` 
WHERE `date` >= '2011-5-4' 
Group by PaymentType

这是一个参考 http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html

Answer 2

看起来不正确，但将COUNT()更改为SUM()可以正常工作：

SELECT COUNT(*) AS countTotal
     , SUM(cost) AS cost
     , SUM(paymentType = 'credit') AS count_credit   --- SUM does counting here
     , SUM(paymentType = 'cash') AS count_cash       --- and here
FROM purchase
WHERE `date` >= '2011-05-04'

解释：True == 1和False == 0用于MySQL。

Answer 3

在WHERE子句

之后需要一个GROUP BY子句

SQL查询没有返回期望结果

3 个答案: