設置一個變量，以識別特定領域在MySQL

Question

來總結我有一個查詢，看起來像這樣：

SELECT 'FY14' AS YEAR, 
SUM(IF(acctcode = 'KAE',sc.bal03,0)) AS NIBD, 
SUM(IF(acctcode = 'GAA',sc.bal03,0)) AS Labor 
FROM summarycurrent AS sc 

sc.bal03是領域於12月值的揚月份當月值存儲在sc.bal04。我有查詢引用sc.bal03多達20次，並更改字段名稱以從不同的月份提取數據是重複的，並且容易出錯。我想使用一個變量來告訴查詢哪個字段總結，但我不明白，如果它甚至是可能的。

我現在的（非功能）查詢看起來是這樣的：

SET @Var:= sc.Bal03; 
SELECT 'FY14' AS YEAR, 
SUM(IF(acctcode = 'KAE',@Var,0)) AS NIBD, 
SUM(IF(acctcode = 'GAA',@Var,0)) AS Labor 
FROM summarycurrent AS sc 

我得到任何FY14, 0, 0作爲結果，或錯誤sc.不在字段列表。 我只想定義sc.Bal03作爲一次總和的字段，而不是多次這樣做。

在此先感謝您的幫助。

Answer 1

，你可以嘗試使用子查詢，並重新命名bal03或bal04爲value這樣

SELECT 'FY14' AS YEAR, 
SUM(IF(acctcode = 'KAE',value,0)) AS NIBD, 
SUM(IF(acctcode = 'GAA',value,0)) AS Labor 
FROM 
(SELECT acctcode, bal03 as value FROM 
summarycurrent 
)as sc 

或

SELECT 'FY14' AS YEAR, 
SUM(IF(acctcode = 'KAE',value,0)) AS NIBD, 
SUM(IF(acctcode = 'GAA',value,0)) AS Labor 
FROM 
(SELECT acctcode, bal04 as value FROM 
summarycurrent 
)as sc 

這樣，你只需要改變bal03或bal04一次。