Question

                SELECT 
                EmailOfConsumer, 
                COUNT(EmailOfConsumer) as 'NumberOfOrders',
                SUM(CAST(Total as money)) as 'TotalValue',
                (SUM(CAST(Total as money))/COUNT(EmailOfConsumer)) as 'AverageValue'
                FROM webshop
                GROUP BY EmailOfConsumer 
                ORDER BY TotalValue DESC

这回来了：

EmailOfConsumer NumberOfOrders  TotalValue                AverageValue
test                   1              2000000000.10           2000000000.10

我想在WHERE NumberOfOrders = '1'

上添加搜索

我尝试添加WHERE COUNT(EmailOfConsumer) = '1'

但是我收到了这个错误：

    An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a 
HAVING clause or a select list, and the column being aggregated is an outer reference.

Answer 1

使用

HAVING COUNT(EmailOfConsumer) = 1

having子句限制聚合，而where子句仅限制单个列数据

Answer 2

使用group by然后具有子句。请参阅this

SELECT 
            EmailOfConsumer, 
            COUNT(EmailOfConsumer) as 'NumberOfOrders',
            SUM(CAST(Total as money)) as 'TotalValue',
            (SUM(CAST(Total as money))/COUNT(EmailOfConsumer)) as 'AverageValue'
            FROM webshop
            GROUP BY EmailOfConsumer 
            HAVING COUNT(EmailOfConsumer) = '1'
            ORDER BY TotalValue DESC

Answer 3

SELECT 
                EmailOfConsumer, 
                COUNT(EmailOfConsumer) as 'NumberOfOrders',
                SUM(CAST(Total as money)) as 'TotalValue',
                (SUM(CAST(Total as money))/COUNT(EmailOfConsumer)) as 'AverageValue'
                FROM webshop
                GROUP BY EmailOfConsumer 

HAVING COUNT(EmailOfConsumer) = '1'
                ORDER BY TotalValue DESC

Answer 4

你可以尝试

SELECT 
            EmailOfConsumer, 
            COUNT(EmailOfConsumer) as 'NumberOfOrders',
            SUM(CAST(Total as money)) as 'TotalValue',
            (SUM(CAST(Total as money))/COUNT(EmailOfConsumer)) as 'AverageValue'
            FROM webshop
            GROUP BY EmailOfConsumer 
            HAVING COUNT(EmailOfConsumer) = 1
            ORDER BY TotalValue DESC

Answer 5

您需要在HAVING clause中添加过滤条件。 COUNT也会返回数值，因此无需添加引号来检查：

SELECT     EmailOfConsumer, 
           COUNT(EmailOfConsumer) as 'NumberOfOrders',
           SUM(CAST(Total as money)) as 'TotalValue',
           (SUM(CAST(Total as money))/COUNT(EmailOfConsumer)) as 'AverageValue'
           FROM webshop
           GROUP BY EmailOfConsumer 
           HAVING COUNT(EmailOfConsumer) = 1
           ORDER BY TotalValue DESC

您无法使用COUNT in WHERE clause检查条件，因为它会在聚合之前执行，因此您需要在HAVING clause中汇总后进行检查。

Answer 6

使用此查询：

SELECT 
    EmailOfConsumer, 
    COUNT(EmailOfConsumer) as 'NumberOfOrders',
    SUM(CAST(Total as money)) as 'TotalValue',
    (SUM(CAST(Total as money))/COUNT(EmailOfConsumer)) as 'AverageValue'
FROM webshop
GROUP BY EmailOfConsumer 
HAVING COUNT(*) = 1
ORDER BY TotalValue DESC

注意：

WHERE子句位于 GROUP BY之前，而HAVING子句位于 GROUP BY
WHERE子句在聚合之前过滤行; HAVING子句过滤聚合行

COUNT(...)会返回一个数字，因此常量1应该不用引号括起来。

查询使用WHERE子句计数记录

6 个答案: