Re: FK issue

On Thu, 2004-06-10 at 17:03, Uwe C. Schroeder wrote:
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> On Thursday 10 June 2004 08:21 am, mike wrote:
> > I have set up a FK as follows
> >
> > ALTER TABLE lk_sub_con ADD FOREIGN KEY (type) REFERENCES
> > lk_sort_of_contact(type_code);
> >
> > However when I do this
> >
> > INSERT INTO lk_sort_of_contact (type_code) VALUES ('1') (ie: a NULL into
> > the FK) it works
> >

this should have said

INSERT INTO lk_sub_con (sub_cat) VALUES ('1') (ie: a NULL into
the FK) it works ie: a NULL in type

(wrong copy)
> > Is this a bug?
>
> No.
> you have a table lk_sub_con. That table has the foreign key assigned.
> This means it doesn't matter what you put into lk_sort_of_contact , it matters
> what you put into lk_sub_con.
> The foreign key says something like
> "If you put a value into field type of table lk_sub_con, the same value must
> be existant in table lk_sort_of_contact field type_code"
>
> Try to add a null value to lk_sub_con.type - or any value that's not in
> lk_sort_of_contact. Postgres will throw an error.

this is the problem - it doesnt if I put a null in (the refernced column
has no nulls)


> If you don't want nulls in the referenced table lk_sort_of_contact you have to
> define that there. Maybe you make the field type_code unique or the primary
> key.
>

It is
>     UC


For info

 SELECT type_code FROM lk_sort_of_contact;  type_code
-----------          3          6          5          1
         2
         4
         7
         9
         8
        10
        11
        12
        13
        14
        16
        17
        20
        21


 SELECT * FROM lk_sub_con;
 sub_id | type | sub_cat | scat_desc
--------+------+---------+-----------
      1 |      |       1 |
      2 |      |      20 |
      3 |   21 |      22 |

(after the above FK & INSERT)


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