Message-ID: <47AC567F.9020907@Sheeky.Biz>
Date: Fri, 08 Feb 2008 23:47:51 +1030
From: Shane Ambler <pgsql@Sheeky.Biz>
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To: Shavonne Marietta Wijesinghe <shavonne.marietta@studioform.it>
CC: pgsql-sql@postgresql.org
Subject: Re: Serial not nulla
References: <00a401c86a43$f88de120$3102a8c0@dream>
In-Reply-To: <00a401c86a43$f88de120$3102a8c0@dream>
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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

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