Limit SQL Server column to a list of possible values

问题

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" or "maybe"
Column Data Type: nvarchar(5)
DBMS: SQL Server 2008

回答1:

you can use a CHECK constraint

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

MSDN link

回答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'))
);

回答3:

Using enumeration table is a way to go.

来源：https://stackoverflow.com/questions/11981868/limit-sql-server-column-to-a-list-of-possible-values