Question

是否可以从MYSQL中的两个别名的剩余部分创建第三个别名？

这是我的问题：

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

我想要做的是创建第三个别名，这个别名是'nextdue'减去'current_cyle'别名的区别？类似的东西：

nextdue - current_cycle AS remainder?

抱歉，如果菜鸟或其他什么。

由于

Answer 1

您不能将计算结果别名用于select部分中的其他计算（http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html）。但是，您可以通过重建查询来获得所需内容，以便它将使用连接和分组：

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

从MYSQL中的两个别名的剩余部分创建第三个别名？

1 个答案: