聚合列

對我的問題summarizing-two-conditions-on-the-same-sql-table跟進的引用MySQL的別名，我添加的比例列，它是一個簡單的SUM（...）列由第二SUM（...）柱分爲：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

它看起來不錯，很乾淨，可以定義這樣的RATIO，但顯然forbidden by SQL。

爲了讓查詢起作用，我只複製了NON_BILLABLE和BILLABLE的CASE語句。

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，更乾淨（非冗餘）的方式來編寫此查詢？

來源

2009-11-24 Eric J.

的問題是，你不能訪問您查詢的選擇子句中的別名（'NON_BILLABLE'和'BILLABLE'）。您只能在WHERE或HAVING子句中引用它們。您*可能*能夠用左連接或其他東西來綁定它，但我不確定。 – keithjgrant 2009-11-24 18:06:52

根據http://stackoverflow.com/questions/942571/using-column-alias-in-where-clause-of-mysql-query-produces-an-error你不能在標準SQL中的WHERE子句中訪問它們。 – 2009-11-24 18:39:03

啊，對！在WHERE子句中只能訪問表別名。 – 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

來源

2009-11-24 18:05:41

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