聚合列

对我的问题summarizing-two-conditions-on-the-same-sql-table跟进的引用MySQL的别名，我添加的比例列，它是一个简单的SUM（...）列由第二SUM（...）柱分为：聚合列

SELECT 
    COMPANY_ID, 
    SUM(CASE WHEN STATUS IN (0, 1) THEN 1 ELSE 0 END) AS NON_BILLABLE, 
    SUM(CASE WHEN STATUS IN (2, 3) THEN 1 ELSE 0 END) AS BILLABLE 
    SUM(NON_BILLABLE)/SUM(BILLABLE) AS RATIO 
FROM TRANSACTIONS 
GROUP BY COMPANY_ID

它看起来不错，很干净，可以定义这样的RATIO，但显然forbidden by SQL。

为了让查询起作用，我只复制了NON_BILLABLE和BILLABLE的CASE语句。

SELECT 
    COMPANY_ID, 
    SUM(CASE WHEN STATUS IN (0, 1) THEN 1 ELSE 0 END) AS NON_BILLABLE, 
    SUM(CASE WHEN STATUS IN (2, 3) THEN 1 ELSE 0 END) AS BILLABLE 
    SUM(CASE WHEN STATUS IN (0, 1) THEN 1 ELSE 0 END)/SUM(CASE WHEN STATUS IN (2, 3) THEN 1 ELSE 0 END) AS RATIO 
FROM TRANSACTIONS 
GROUP BY COMPANY_ID

是否有更好，更干净（非冗余）的方式来编写此查询？

来源

2009-11-24 Eric J.

的问题是，你不能访问您查询的选择子句中的别名（'NON_BILLABLE'和'BILLABLE'）。您只能在WHERE或HAVING子句中引用它们。您*可能*能够用左连接或其他东西来绑定它，但我不确定。 – keithjgrant 2009-11-24 18:06:52

根据http://stackoverflow.com/questions/942571/using-column-alias-in-where-clause-of-mysql-query-produces-an-error你不能在标准SQL中的WHERE子句中访问它们。 – 2009-11-24 18:39:03

啊，对！在WHERE子句中只能访问表别名。 – keithjgrant 2009-11-24 18:46:00

用途：

SELECT x.company_id, 
     x.non_billable, 
     x.billable, 
     x.non_billable/x.billable AS RATIO 
    FROM (SELECT t.company_id 
       SUM(CASE WHEN STATUS IN (0, 1) THEN 1 ELSE 0 END) AS NON_BILLABLE, 
       SUM(CASE WHEN STATUS IN (2, 3) THEN 1 ELSE 0 END) AS BILLABLE 
     FROM TRANSACTIONS 
    GROUP BY t.company_id) x

来源

2009-11-24 18:05:41

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