Re: Using column aliasses in the same query

On 17 apr 2011, at 13:21, Leif Biberg Kristensen wrote:

> On Sunday 17 April 2011 13:01:45 Robert J.C. Ivens wrote:
>> Hi,
>>
>> I am not sure if there ever was a feature request for using defined column
>> aliases in the rest of a query. This would make queries with a lot of
>> logic in those aliased columns a lot smaller and this easier to
>> write/debug.
>>
>> I already know you can use the following syntax:
>>
>> SELECT col1, col2, col3, (col2-col3) as col4 FROM (SELECT col1, (long and
>> lots of logic here) as col2, col3 FROM table) s WHERE col2 < aValue
>>
>> But when you need to use (calculated) values from the actual record and or
>> have sub-selects in your main select that also need to use these values
>> things get really hairy. I don't know if the SQL specification allows it
>> but I know that RDBMS's like Sybase already support this.
>>
>> Any thoughts?
>
> It's easy to define a view or an SQL function and stash the hairy logic there.
>
> regards, Leif

True, but that is essentially the same thing as the example query I gave.
There are plenty of cases where this approach is not workable.

Cheers,
Robert