--On Thursday, September 25, 2003 20:09:35 +0100 Richard Huxton
<dev@archonet.com> wrote:
> On Thursday 25 September 2003 19:51, Larry Rosenman wrote:
>> I have the following rows (in addition to others):
>>
>> acct_num text,
>> master_acct_num text,
>>
>>
>> These are in the same table.
>>
>> What I want to enforce is that if the master_acct_num field is NOT NULL
>> (it can be NULL, and
>> that's fine), that the value appears in some row as acct_num. acct_num
>> has a unique index on it, so that's fine.
>>
>> I'm not sure how to do this....
>
> ALTER TABLE my_table ADD CONSTRAINT my_self_fk FOREIGN KEY
> (master_acct_num) REFERENCES my_table (acct_num);
>
> It's really just a foreign-key to yourself
I wasn't sure I could do that. Thanks!
LER
--
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 972-414-9812 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749