Limit SQL Server column to a list of possible values

Using enumeration table is a way to go.

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'))
);

you can use a CHECK constraint

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

MSDN link

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