Re: can a foreign key allow null

* Keith Worthington <keithw@narrowpathinc.com> [2004-10-19 15:01:40 -0400]:

>                 Table "myschema.tbl_part"
>         Column        |          Type          | Modifiers
> ----------------------+------------------------+-----------
>  sales_gl_account     | character varying(15)  |
>
>         Table "myschema.tbl_gl_account"
>    Column    |         Type          | Modifiers
> -------------+-----------------------+-----------
>  number      | character varying(15) | not null
>
> Is it possible to create a foreign key such that only null and
> values from myschema.tbl_gl_account.number are allowed in
> myschema.tbl_part.sales_gl_account?

How is this any different than a regular foreign key constraint?

ALTER TABLE tbl_part ADD CONSTRAINT account_number_exists FOREIGN KEY
(sales_gl_account) REFERENCES tbl_gl_account(number);

HTH,

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