Does adding a CHECK CONSTRAINT apply only to future data modifications?

[#1]

Testing with v12.0.1.3726 on Windows, I'm somewhat surprised that an ALTER TABLE ADD CONSTRAINT CHECK (whatsoever) does not seem to fail when the underlying data won't satisfy the check.

I would have bet it is the other way, i.e. it is not possible to add a table check constraint when the existing data violate the check condition. - But I seem to be wrong...

Does that mean adding a CHECK CONSTRAINT (here a table) will not check the existing table data, whereas adding a PRIMARY/UNIQUE KEY or an FOREIGN KEY surely does check the entity/referential integrity (and will fail accordingly) - so the check will only apply to future DML statements?

(Note: The according table check does work for future modifications, so it's not the particular check condition that might be wrong...)

[jeff_albion]

Hi Volker,

I have opened CR #711831 for this enhancement suggestion for the ALTER TABLE ADD [WITH { CHECK | NOCHECK } ] CONSTRAINT ... CHECK syntax to be considered in a future SQL Anywhere release. Thank you for the product suggestion!