Thread: Parameter for query

Is there any way to set a variable or parameter for a query?

I have a long query where a certain variable needs to be easy to
change.  I'd like to do something like:

threshold = 10.3

SELECT... WHERE x > $threshold... AND y * 1.3 > $threshold...

Currently, I need to do this in a scripting language.  Is there a
straightforward way to do this directly in Postgres?

On Wed, Jul 17, 2013 at 1:25 PM, Robert James <srobertjames@gmail.com> wrote:
> Is there any way to set a variable or parameter for a query?
>
> I have a long query where a certain variable needs to be easy to
> change.  I'd like to do something like:
>
> threshold = 10.3
>
> SELECT... WHERE x > $threshold... AND y * 1.3 > $threshold...
>
> Currently, I need to do this in a scripting language.  Is there a
> straightforward way to do this directly in Postgres?
Using which client? psql? In this case there is that:
http://www.postgresql.org/docs/devel/static/app-psql.html#APP-PSQL-INTERPOLATION

postgres=# \set foo 1
postgres=# select :foo;
 ?column?
----------
        1
(1 row)

mpaquier=# \set foo bar
mpaquier=# select :'foo';
 ?column?
----------
 bar
(1 row)

Regards,
--
Michael

On Wed, Jul 17, 2013 at 6:25 AM, Robert James <srobertjames@gmail.com> wrote:
> Is there any way to set a variable or parameter for a query?
>
> I have a long query where a certain variable needs to be easy to
> change.  I'd like to do something like:
>
> threshold = 10.3
>
> SELECT... WHERE x > $threshold... AND y * 1.3 > $threshold...
>

Using prepared statements? See here:
http://www.postgresql.org/docs/9.2/static/sql-prepare.html


> Currently, I need to do this in a scripting language.  Is there a
> straightforward way to do this directly in Postgres?

well, if you are doing this in a script(ing) it should be quite easy
to do string interpolation.

Luca