On 14 Jul 2010, at 18:13, David Kerr wrote:
> Howdy,
>
> I'm trying to think of the best way to handle this situation.
>
> I've got 2 tables, X and Y
>
> Table X has a field foo varchar(20)
> Table Y has a field bar varchar(20)
>
> I want to enforce, that if table X.foo = 'dave' then you can't insert (or
> update) Y.bar = 'dave'
You could add a table Z (
baz varchar(20) PRIMARY KEY,
foo varchar(20) REFERENCES X (foo),
bar varchar(20) REFERENCES Y (bar),
CHECK ((foo IS NULL AND bar IS NOT NULL) OR (foo IS NOT NULL AND bar IS
NULL))
)
You can populate this table from a rule or trigger.
OTOH, if you have a trigger anyway, you can move the checks in there as well.
Alban Hertroys
--
If you can't see the forest for the trees,
cut the trees and you'll see there is no forest.
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