Limit SQL Server column to a list of possible values

Question

How do I put a constraint on a column so that it can only contain the following values? What do you call this type of constraint?

Allowed values: \"yes\", \"no\"         


        

Answer 1

you can use a CHECK constraint

ALTER TABLE <table>
ADD CONSTRAINT chk_val CHECK (col in ('yes','no','maybe'))

MSDN link

Answer 2

Yes, check a constraint is it what you need. You can declare check constraint at the table declaration:

CREATE TABLE test(
    _id BIGINT PRIMARY KEY NOT NULL,
    decision NVARCHAR(5),
    CHECK (decision in ('yes','no','maybe'))
);

Answer 3

Using enumeration table is a way to go.