unique constraint ignorujici NULL

[Vaclav Ovsik]

On Tue, Aug 07, 2001 at 08:03:26AM +0200, Michal Polák wrote:
> Dobry den vespolek,
> 
> vite nekdo o databazovem stroji, kde by bylo mozne nadefinovat constraint,
> ktery by jednoduse umoznoval, aby byla ve sloupci unikatni NENULL hodnota,
> nebo NULL ?
> 
> Uznavam, ze cistsi postup by asi byl zavedenim triggeru.
> Ale tim contraintem by se nektere veci zjednodusily....
> A to nemluvim o vykonnosti.
> 
> Dekuji.
> --
> Michal Polak
> system programmer, TurboConsult s.r.o.
> mpolak na email.cz, michal.polak na turboconsult.cz
> ICQ: 106342077
> Tel:+420 5 4121 2898
> 
> Everyone should hold strong convictions, I am convinced I will have another
> glass.
> 

Ono to nejde ?

U me na PostgreSQL 7.1.2:

test=# create table neco (x text unique null);
NOTICE:  CREATE TABLE/UNIQUE will create implicit index 'neco_x_key' for table 'neco'
CREATE
test=# insert into neco values ('ahoj');
INSERT 139883 1
test=# insert into neco values ('ahoj');
ERROR:  Cannot insert a duplicate key into unique index neco_x_key
test=# insert into neco values ('nazdar');
INSERT 139885 1
test=# insert into neco values ('nazdar');
ERROR:  Cannot insert a duplicate key into unique index neco_x_key
test=# insert into neco values (null);
INSERT 139887 1
test=# insert into neco values (null);
INSERT 139888 1
test=# insert into neco values (null);
INSERT 139889 1
test=# select * from neco;
   x    
--------
 ahoj
 nazdar
 
 
 
(5 rows)

test=# 


-- 
	Vaclav Ovsik		email: Vaclav.Ovsik na i.cz
	ICZ a.s.		phone: +420 19 7488511
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