從MYSQL中兩個別名的其餘部分創建第三個別名？

Question

是否可以從MYSQL中的兩個別名的其餘部分創建第三個別名？

這裏是我的查詢：

SELECT DISTINCT 
workcards.task, 
workcards.program, 
workcards.zone, 
workcards.CYLcomp, 
workcards.CYLint, 
workcards.task, 
workcards.CYLcomp + workcards.CYLint AS nextdue, 
workcards.wcnumber, 
(SELECT airtimes.total_cycles 
     FROM airtimes 
     WHERE airtimes.nnumber='xxxxx' 
     ORDER BY airtimes.total_cycles DESC LIMIT 1) AS current_cycle 
FROM workcards 
WHERE basis LIKE '%CYL%' 
AND nnumber='xxxxx' 
ORDER BY CASE nextdue 
WHEN 0 THEN 1 ELSE -1 END ASC, nextdue ASC 

我想要做的就是創建第三別名這將是「nextdue」減「current_cyle」別名的區別？例如：

nextdue - current_cycle AS remainder? 

對不起，如果noob或任何。

感謝

Answer 1

不能使用計算結果別名select部分與其他計算中使用（http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html） 。但你可以通過重建你的查詢來得到你想要的，所以它會使用連接和分組：

SELECT DISTINCT 
    w.*, 
    w.CYLcomp + w.CYLint AS nextdue, 
    MAX(a.total_cycles) AS current_cycle 
    w.CYLcomp + w.CYLint - MAX(a.total_cycles) AS reminder 
FROM workcards w 
JOIN airtimes a ON a.nnumber = w.nnumber 
WHERE w.basis LIKE '%CYL%' AND w.nnumber='xxxxx' 
GROUP BY w.nnumber 
ORDER BY CASE nextdue WHEN 0 THEN 1 ELSE -1 END ASC, nextdue ASC