Обсуждение: Simple SQL

Is it possible to do something like:

    select 1 as a, a*a;

in postgres?

Not

SELECT 1 as a, a*2;
ERROR:  column "a" does not exist

Regards
Pavel


On Tue, 21 Oct 2003, Bob Messenger wrote:

> Is it possible to do something like:
>
>     select 1 as a, a*a;
>
> in postgres?
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match
>

On Fri, Oct 24, 2003 at 07:25:44AM +0200, Pavel Stehule wrote:
> Not
>
> SELECT 1 as a, a*2;
> ERROR:  column "a" does not exist

But you can try

SELECT a, a*a FROM (select 1 as a);

> On Tue, 21 Oct 2003, Bob Messenger wrote:
>
> > Is it possible to do something like:
> >
> >     select 1 as a, a*a;
> >
> > in postgres?

--
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
"Hay que recordar que la existencia en el cosmos, y particularmente la
elaboración de civilizaciones dentre de él no son, por desgracia,
nada idílicas" (Ijon Tichy)

Alvaro Herrera wrote:
> On Fri, Oct 24, 2003 at 07:25:44AM +0200, Pavel Stehule wrote:
>
>>Not
>>
>>SELECT 1 as a, a*2;
>>ERROR:  column "a" does not exist
>
>
> But you can try
>
> SELECT a, a*a FROM (select 1 as a);
>
>
>>On Tue, 21 Oct 2003, Bob Messenger wrote:
>>
>>
>>>Is it possible to do something like:
>>>
>>>    select 1 as a, a*a;
>>>
>>>in postgres?
>
>

alien=# SELECT a, a*a FROM (select 1 as a);
ERROR:  sub-SELECT in FROM must have an alias
         For example, FROM (SELECT ...) [AS] foo

Thanks for idea though.  It led me to this:

alien=# SELECT a, a*a FROM (SELECT 2 AS a) AS a;
  a | ?column?
---+----------
  2 |        4
(1 row)