Обсуждение: Expr Abbreviations/Functions?

I find myself frequently typing (postgresql-6.5.1) the following:
 SELECT * FROM table  WHERE (f1 ~* 'foo' OR f2 ~* 'foo' OR f3 ~* 'foo');

Can "CREATE FUNCTION" be used?  Something like
 CREATE FUNCTION f(string)  RETURNS bool  AS '(f1 ~* '$1' OR f2 ~* '$1' ...)';

and then type
 SELECT * FROM table WHERE f('foo');


I tried to define such a function, but encountered two problems:
o It didn't "accept" the function's definition
o Syntax errors (apostrophes need escaping ... I tried mixing quotes  and apostrophes, also using '\' chars ... nothing
seemedto work)
 


I know that I can define VIEWs (and FUNCTIONs) that contain a specific
SELECT statement, but I'd prefer to have definitions of just the
repeating expressions.


Another thing I'd like to "abbreviate" is the second phrase in
SELECTs. E.g,
SELECT x FROM table;

instead of
SELECT x1,x2,x3 FROM table;

where 'x' is somehow equivalent to 'x1,x2,x3'.


I read the online docs and searched a few SQL books, but can't seem to
find the correct approach.  Ideas?

Thanks for any help,

-Prof Kenneth H Jacker       khj@cs.appstate.edu
-Computer Science Dept       www.cs.appstate.edu/~khj
-Appalachian State Univ
-Boone, NC  28608  USA        

Kenneth,

You could merge the fields and search with :

select * from tablex where lower(f1||f2||f3) ~ 'foo';




Troy

Troy Korjuslommi                Tksoft OY, Inc.
tjk@tksoft.com                  Software Development
                                Open Source Solutions
                                Hosting Services




>
> I find myself frequently typing (postgresql-6.5.1) the following:
>
>   SELECT * FROM table
>    WHERE (f1 ~* 'foo' OR f2 ~* 'foo' OR f3 ~* 'foo');
>
> Can "CREATE FUNCTION" be used?  Something like
>
>   CREATE FUNCTION f(string)
>    RETURNS bool
>    AS '(f1 ~* '$1' OR f2 ~* '$1' ...)';
>
> and then type
>
>   SELECT * FROM table WHERE f('foo');
>
>
> I tried to define such a function, but encountered two problems:
>
>  o It didn't "accept" the function's definition
>
>  o Syntax errors (apostrophes need escaping ... I tried mixing quotes
>    and apostrophes, also using '\' chars ... nothing seemed to work)
>
>
> I know that I can define VIEWs (and FUNCTIONs) that contain a specific
> SELECT statement, but I'd prefer to have definitions of just the
> repeating expressions.
>
>
> Another thing I'd like to "abbreviate" is the second phrase in
> SELECTs. E.g,
>
>     SELECT x FROM table;
>
> instead of
>
>     SELECT x1,x2,x3 FROM table;
>
> where 'x' is somehow equivalent to 'x1,x2,x3'.
>
>
> I read the online docs and searched a few SQL books, but can't seem to
> find the correct approach.  Ideas?
>
> Thanks for any help,
>
> -Prof Kenneth H Jacker       khj@cs.appstate.edu
> -Computer Science Dept       www.cs.appstate.edu/~khj
> -Appalachian State Univ
> -Boone, NC  28608  USA
>
>
>
>

At 02:11 +0300 on 25/07/1999, tjk@tksoft.com wrote:


> You could merge the fields and search with :
>
> select * from tablex where lower(f1||f2||f3) ~ 'foo';

Nah. If f1 is 'Narf' and f2 is 'oodp', it will match...

Herouth

--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma

Herouth,

You're right.

If I recall the original question correctly, the
"only" real solution would seem to be to define
a function to search the appropriate fields.


Troy

Troy Korjuslommi                Tksoft OY, Inc.
tjk@tksoft.com                  Software Development
                                Open Source Solutions
                                Hosting Services





>
> At 02:11 +0300 on 25/07/1999, tjk@tksoft.com wrote:
>
>
> > You could merge the fields and search with :
> >
> > select * from tablex where lower(f1||f2||f3) ~ 'foo';
>
> Nah. If f1 is 'Narf' and f2 is 'oodp', it will match...
>
> Herouth
>
> --
> Herouth Maoz, Internet developer.
> Open University of Israel - Telem project
> http://telem.openu.ac.il/~herutma
>
>
>
>

At 07:52 +0300 on 26/07/1999, tjk@tksoft.com wrote:


> If I recall the original question correctly, the
> "only" real solution would seem to be to define
> a function to search the appropriate fields.

Yes. The original question had a conceptual problem. It wanted to
abbreviate the expression without the name of the table. This was
nonsensical - you can't ask whether id > 3. You can ask whether person.id >
3. Just "id" could be anything in the world. Asking a database to do that
is like asking a person to play a flute in vacuum.

Another problem was that it implied returning a set of rows. This is not
well supported by postgres - and that's a known limitation.

The best thing that can be done at the moment is to have a function that
accepts the strings as parameters and returns a boolean:

CREATE FUNCTION match_three ( text, text, text, text ) RETURNS bool AS ' SELECT (( $1 ~ $4 ) OR ( $2 ~ $4 ) OR ($3 ~
$4))
' LANGUAGE 'sql';

Then it can be used as:

SELECT * FROM table1
WHERE match_three( x1, x2, x3, 'foo' );

Herouth

--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma