将MySQL别名字段添加到一起

Question

考虑类似于以下内容的查询：

 SELECT sum(EXPR) as total,
        sum(EXPR) as total2, 
        sum(total+total2) as grandtotal 
 FROM tablename

这将显示字段列表中的未知列总数。

在不重新键入sum表达式的情况下，是否可以在计算中引用别名字段，因为两边的sum(EXPR)都很长。

Answer 1

SELECT total, total2, total + total2 as grandtotal from (
 SELECT sum(EXPR) as total, 
        sum(EXPR) as total2,  
 FROM tablename 
) x

Answer 2

SELECT
WITH Sums AS
(
 SELECT sum(EXPR) as total, 
        sum(EXPR) as total2
 FROM tablename 
)
SELECT SUM(sums);

对于你们这些tsql的粉丝..。

Answer 3

你可以使用变量：

http://dev.mysql.com/doc/refman/5.0/en/user-variables.html