MySQL Bugs: #14721: Should be allowed to reference column alias in another column expression

Bug #14721	Should be allowed to reference column alias in another column expression
Submitted:	7 Nov 2005 20:52	Modified:	14 Jun 2013 18:23
Reporter:	Mike MySQLAB	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Optimizer	Severity:	S4 (Feature request)
Version:	4.1	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Column aliases cannot be referenced in the column list and I think that is wrong. I have complicated expressions in the column list and I'd like to reference them in other column expressions. As it stands, I have to repeat the expressions which can lead to mistakes if I don't update the expressions in both locations. Having the same column expressions in more than one location makes the query much harder to read.

How to repeat:
For example, the following should work but doesn't:
select 1+2 col1, 3+4 col2, col1+col2;

It complains "unknown column col1" in columns list. 

Suggested fix:
Why isn't MySQL smart enough to either reference col1, or copy the col1 expression internally for use by col1+col2?