Re: can a foreign key allow null

* Keith Worthington <keithw(at)narrowpathinc(dot)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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