Is there an sql constraint that enables you to disallow certain values in a column?
e.g.
ALTER TABLE foo ADD COLUMN code TEXT NOT NULL UNIQUE DISALLOW '<GENERATE>' ; s.t. <GENERATE> could be used safely in the application to indicate that the value should be generated before persisting without risking its accidentally being pushed to DB?
You need a check constraint:
ALTER TABLE foo ADD COLUMN code TEXT NOT NULL UNIQUE; alter table foo add constraint disallow_generate check (code <> '<GENERATE>'); If you want to disallowed multiple values, use a NOT IN condition:
alter table foo add constraint disallow_generate check (code not in ('<GENERATE>', '<GENERATED>', 'foo'); You could use Check Constraints. eg:
ALTER TABLE foo ADD COLUMN code TEXT NOT NULL UNIQUE CHECK (code <> '<GENERATE>'); 