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Re: how to concatenate in PostgreSQL

From: Steve Crawford <scrawford(at)pinpointresearch(dot)com>
To: Rehan Saleem <pk_rehan(at)yahoo(dot)com>
Cc: sql pgsql <pgsql-sql(at)postgresql(dot)org>
Subject: Re: how to concatenate in PostgreSQL
Date: 2012-03-27 16:12:47
Message-ID: 4F71E6FF.6060204@pinpointresearch.com (view raw or flat)
Thread:
Lists: pgsql-sql
On 03/27/2012 07:48 AM, Rehan Saleem wrote:
> well i am quite sure its PostgreSQL forum and it is obvious, i am 
> asking this to concatenate in plpgsql.
> ------------------------------------------------------------------------
> *From:* Steve Crawford <scrawford(at)pinpointresearch(dot)com>
> *To:* pgsql-sql(at)postgresql(dot)org
> *Sent:* Monday, March 26, 2012 9:08 PM
> *Subject:* Re: [SQL] how to concatenate in PostgreSQL
>
> On 03/24/2012 04:43 AM, Rehan Saleem wrote:
>> hi ,
>> how can we concatinate these lines and execute sql command
> In what? Psql? A PL/pgSQL function. C/Java/PHP/Python/Perl/Erlang/Lua?
>>        setsql = 'select user,username, firstname '
>>       set sql += ' lastname, cardno from table1 where userid=' + 5
>>       exec(sqi)
>>      where 5 is the userid from table1
>> thanks
>>
> Cheers,
> Steve
>
>
Yes, after about a decade of PostgreSQL use and forum participation I 
think I know which forum this is. Sarcasm and biting at people who want 
to help you is not a good way to make friends and get help on the forums.

If you meant PL/pgSQL then say it. It is not the same as SQL though the 
syntax is generally similar. Look at DECLARE and BEGIN for starters. 
I've seen too many threads get reset back to the start once some 
incorrect assumptions get corrected to feel that up-front clarification 
is a waste of time. 
http://wiki.postgresql.org/wiki/Guide_to_reporting_problems is more 
oriented to problem reporting than general questions but has helpful 
advice nonetheless.

Back to the issue at hand...others have pointed out the || operator and 
the issue with NULL. It appears you are doing a lot of conversion 
requiring writing of PL/pgSQL functions. Spend a few minutes skimming:
http://www.postgresql.org/docs/current/static/plpgsql.html

As to the topic of executing the command including many examples see:
http://www.postgresql.org/docs/current/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN

If you are writing functions that must use dynamically generated table 
and column names, become familiar with the quote_ident, quote_literal 
and quote_nullable functions.

Cheers,
Steve

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