----- Original Message -----
From: "ivan marchesini" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, September 24, 2007 6:04 PM
Subject: [SQL] foreign key problem
Dear users,
I'm trying to create constraints into a db they give me from access...
I'm using pgadmin to create a new foreign key for the relationship
between two table..
I have a table called "generalita" wich contains a column called
"cod_carg":
___________________
select cod_carg from generalita group by cod_carg;
cod_carg
----------
2
0
1
(4 righe)
___________________
I have another table, called "diz_carg" that contain, into a column
called "cod_carg" (that is a primary key), the domain values for the
"cod_carg" column of "generalita":
__________________
select cod_carg from diz_carg group by cod_carg;
cod_carg
----------
1
0
2
(3 righe)
__________________
so when I try to create the foreign key I obtain:
ALTER TABLE generalita ADD CONSTRAINT fkey_diz_cod_carg FOREIGN KEY
(cod_carg) REFERENCES diz_carg (cod_carg) ON UPDATE NO ACTION ON DELETE
NO ACTION;
____________________________
ERROR: insert or update on table "generalita" violates foreign key
constraint "fkey_diz_cod_carg"
DETAIL: Key (cod_carg)=( ) is not present in table "diz_carg".
____________________________
can I allow null values for "generalita.cod_carg" although it is a
foreign key for "diz_carg.cod_carg"?
I apologize if it is a stupid question.... :-(
many thanks to all
Yes you can , check that column cod_carg of table generalita is not set to
NOT NULL.
With regards Ashish
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
