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Re: Function PostgreSQL 9.2

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On 05/03/2016 02:27 PM, drum.lucas@xxxxxxxxx wrote:


On 4 May 2016 at 01:18, Melvin Davidson <melvin6925@xxxxxxxxx
<mailto:melvin6925@xxxxxxxxx>> wrote:



    On Tue, May 3, 2016 at 1:21 AM, David G. Johnston
    <david.g.johnston@xxxxxxxxx <mailto:david.g.johnston@xxxxxxxxx>> wrote:


            Well.. I don't need to add a constraint if I already have a
            default value, that's right...


        Wrong
        David J.


    What you need is a TRIGGER function & TRIGGER that will select  and
    assign the next users_code based on company_id.
    I'm not going to write the whole thing for you, but here is part of
    the trigger function logic.

    eg: IF NEW.company_id = 1 THEN
                   NEW.users_code = NEXTVAL(c1_users_code_seq);
           ELSEIF NEW.company.id <http://NEW.company.id> = 2 THEN
                   NEW.users_code =  NEXTVAL(c2_users_code_seq);
           ELSEIF NEW.company.id <http://NEW.company.id> = 3 THEN
                   NEW.users_code =  NEXTVAL(c3_users_code_seq);
           ...
           ...
           ELSE
               <    something bad happened because NEW.company_id was
    not valid ?
           END IF;




Do I have to have one sequence peer company_id ? There will be
thousands.. isn't there a better way to do that?

    Seriously, get yourself the books I have recommended and study them
    BEFORE you continue attempting to design your database.
    You need a firm understanding of logical design & flow, otherwise
    you will be wasting your time.


That's what I'm doing.. Studying.. asking for some help to get a better
understand.... isn't this the purpose of this mail list?

I think the intent being expressed was to: study --> sketch out design/schema --> ask list whether previous is correct --> make corrections or not --> implement.

Instead what seems to have happened is: implement --> get painted into corner --> ask how to escape corner. Hence the frustration on the part of list members.



--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx


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