Re: select 3 characters

--- Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> CJ -
>
> You might want to join the NOVICE list and post this
> kind of question there,
> should you have more.
>
> > Hi I need select the first 3 characters from a
> table
> >
> > I try this but doesn't work
> >
> > "SELECT left(data,3) AS value FROM table;"
> >
> > i see the left function doesn't work what is the
> similar function in
> postgresql
>
> SUBSTR(data, 1, 3)
>
> See "Functions And Operators" in the online docs for
> more.

PostgreSQL lets you define your own functions, so you
could do something like:

CREATE OR REPLACE FUNCTION left(text, integer) RETURNS
text AS '
SELECT substr($1, 1, $2);
' LANGUAGE 'SQL';

If you have a lot of code already written using the
"left" function, that will save you from having to
rewrite it.

Look at "CREATE FUNCTION" in the "SQL Commands"
section of the manual; also "Procedural Languages" in
the "Programmers Guide". Do a search on "function
overloading", so you will be able to define a function
that works regardless of the datatypes fed to it.

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