This is accomplished with a CHECK constraint. Here's an example:
create table documents
( id integer not null primary key
, title varchar(99) not null
, added date not null
, constraint only_new_ones
check ( added >= '2007-01-01' )
);
The CHECK constraint should always be given a descriptive name, because this
helps identify the source of the error when the constraint is violated. The
constraint name is optional, but the difference
is between getting an error message that looks like this:
INSERT statement terminated. CHECK constraint "CK__documents__added__73852659" was violated.
and one that looks like this:
INSERT statement terminated. CHECK constraint "only_new_ones" was violated.
Use a constraint name that describes the constraint accurately.
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