查询计数记录用WHERE子句

   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

此带回：查询计数记录用WHERE子句

EmailOfConsumer NumberOfOrders TotalValue    AverageValue 
test     1    2000000000.10   2000000000.10

我想在WHERE NumberOfOrders = '1'

添加一个搜索我曾尝试加入WHERE COUNT(EmailOfConsumer) = '1'

，但我得到此错误：

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.

来源

2013-11-20 neeko

为什么将数值与字符串进行比较？例如，'COUNT'返回一个'INT'，并将它与'1'比较而不是'1'是特有的。比较空的字符串更奇怪。 – HABO

使用

HAVING COUNT(EmailOfConsumer) = 1

having子句限制了聚合，而只能在where子句出台限制有关个人列数据

来源

2013-11-20 14:21:09

或者添加“HAVING TotalValue/AverageValue = 0”。顺便说一句：我建议不要使用'1'作为值，而是使用实数1（无'），否则MySQL会投射字符串，效率会降低。此外，HAVING非常慢，在查询完成处理后它可以工作 - 所以使用它被认为是不好的做法。 – nrathaus

在GROUP BY子句之后添加HAVING子句并在ORDER BY –

之前添加HAVING子句@JackJiang只有在值不为空时才知道如何添加此HAVING子句？ – neeko

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

来源

2013-11-20 14:21:19 sh1ng

您可以尝试

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

来源

2013-11-20 14:21:58 vkamayiannis

您需要添加过滤条件在HAVING clause。 也算回报率的数值，以便无需添加引号，以检查它：

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

你不能COUNT in WHERE clause检查条件，因为它会聚集之前执行，所以你需要聚集后，检查它HAVING clause。

来源

2013-11-20 14:22:14

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：

WHERE条款之前GROUP BY，而HAVING条款如下GROUP BY
WHERE条款一个过滤器之前行ggregation; HAVING子句过滤器汇总行

COUNT(...)返回一个数字，所以常量1应该而不是被括在引号中。

来源

2013-11-20 14:23:41 dasblinkenlight

使用group by，然后使用子句。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

来源

2013-11-20 14:23:54 DevelopmentIsMyPassion

查询计数记录用WHERE子句

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