Re: select function alias

----- Original Message -----

> From: "Howard News" <howardnews(at)selestial(dot)com>
> Sent: Wednesday, November 30, 2016 9:03:28 AM
> Subject: Re: [GENERAL] select function alias

> On 30/11/2016 13:42, Timoteo Blanco wrote:

> > I've a series of timestamp columns I'd like to alias in select statements.
> > psql indicates my alias doesnt exist after
>
> > I define it.
>

> > Example -> select to_char(impressions_create_date,'yyyy-mm-dd') as ymd from
> > impressionsdb where ymd like '2016-11%' ;
>

> > psql always complains column ymd does not exist. I've inherited a series of
> > tables with many timestamps and would like to
>
> > shorten the select in queries without renaming any columns.
>

> 3 options:

> 1. Use the same to_char expression in the where clause
> 2. Use a sub-select to use the alias in the outer where clause
> 3. Use the original column in the where clause and use the timestamp
> comparisson functions.

4. Define views on the tables. Make the views writeable using rules.

5. Use a CTE:

with shortnames as (
select to_char(impressions_create_date,'yyyy-mm-dd') as ymd from impressionsdb
) select ymd from shortnames where ymd like '2016-11%';

-- B