查詢計數記錄用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

此帶回：查詢計數記錄用WHERE子句

EmailOfConsumer NumberOfOrders TotalValue    AverageValue 
test     1    2000000000.10   2000000000.10

我想在WHERE NumberOfOrders = '1'

添加一個搜索我曾嘗試加入WHERE COUNT(EmailOfConsumer) = '1'

，但我得到此錯誤：

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.

來源

2013-11-20 neeko

爲什麼將數值與字符串進行比較？例如，'COUNT'返回一個'INT'，並將它與'1'比較而不是'1'是特有的。比較空的字符串更奇怪。 – HABO

使用

HAVING COUNT(EmailOfConsumer) = 1

having子句限制了聚合，而只能在where子句出臺限制有關個人列數據

來源

2013-11-20 14:21:09

或者添加「HAVING TotalValue/AverageValue = 0」。順便說一句：我建議不要使用'1'作爲值，而是使用實數1（無'），否則MySQL會投射字符串，效率會降低。此外，HAVING非常慢，在查詢完成處理後它可以工作 - 所以使用它被認爲是不好的做法。 – nrathaus

在GROUP BY子句之後添加HAVING子句並在ORDER BY –

之前添加HAVING子句@JackJiang只有在值不爲空時才知道如何添加此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

來源

2013-11-20 14:21:19 sh1ng

您可以嘗試

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

來源

2013-11-20 14:21:58 vkamayiannis

您需要添加過濾條件在HAVING clause。 也算回報率的數值，以便無需添加引號，以檢查它：

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檢查條件，因爲它會聚集之前執行，所以你需要聚集後，檢查它HAVING clause。

來源

2013-11-20 14:22:14

使用此查詢：

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條款之前GROUP BY，而HAVING條款如下GROUP BY
WHERE條款一個過濾器之前行ggregation; HAVING子句過濾器彙總行

COUNT(...)返回一個數字，所以常量1應該而不是被括在引號中。

來源

2013-11-20 14:23:41 dasblinkenlight

使用group by，然後使用子句。請參閱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

來源

2013-11-20 14:23:54 DevelopmentIsMyPassion

查詢計數記錄用WHERE子句

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