Re: Serial not nulla

Thanks alot Shane..Just what I wanted.. Didn't think of a solution with 3 
primary keys.

Have a nice day ^___^


Shavonne Wijesinghe
www.studioform.it


----- Original Message ----- 
From: "Shane Ambler" <pgsql@Sheeky.Biz>
To: "Shavonne Marietta Wijesinghe" <shavonne.marietta@studioform.it>
Cc: <pgsql-sql@postgresql.org>
Sent: Friday, February 08, 2008 2:17 PM
Subject: Re: [SQL] Serial not nulla


> Shavonne Marietta Wijesinghe wrote:
>> Hello
>>
>> I am working with a database that has a Index number defined as Serial 
>> NOT NULL
>>
>> I used this because,
>> 1. I want to make sure that when many users login at the same time the 
>> Index number won't be repeated.
>> 2. I don't have to increment it by programming (I use ASP)
>>
>> But now i have a situation that i need to index numbers. For Example i 
>> could have a structure like this
>>
>> INDEX1 - N_SHEET - TOT_SHEET
>> 1 - 1 - 1
>> 2 - 1 - 3
>> 2 - 2 - 3
>> 2 - 3 - 3
>>
>> N_SHEET and TOT_SHEET are filled by the user (via web) but i need to hold 
>> on to the INDEX. And while userA is filling the 3 row if userB loggs in i 
>> need to provide the INDEX1 with 3.
>>
>> Any idea??
>>
>
> As well as using the "Serial NOT NULL" you have also defined this column 
> as PRIMARY KEY (or a unique index) which is what is preventing the 
> duplicates in that column. (A primary key is enforced with a unique index)
>
>
> From the sample shown you can use all three columns as the primary key 
> with something similar to -
>
> ALTER TABLE my_user_sheets DROP CONSTRAINT my_user_sheets_pkey;
> ALTER TABLE my_user_sheets ADD PRIMARY KEY ("INDEX1", "N_SHEET", 
> "TOT_SHEET");
>
> (this implies that for each user they will have only one row for each 
> combination of N_SHEET and TOT_SHEET) If you need to allow them to select 
> the same 2 sheet numbers more than once then I would suggest you have an 
> extra column for a primary key and redefine INDEX1 as the user_id. (or 
> just add a user_id column and leave the INDEX1 as it is)
>
>
>
> It's not recommended but you could also have the table without a primary 
> key allowing duplicate value combinations. This would prevent you updating 
> a single row though.
>
>
>
> -- 
>
> Shane Ambler
> pgSQL (at) Sheeky (dot) Biz
>
> Get Sheeky @ http://Sheeky.Biz