Re: How to restrict

On 2/26/19 9:11 AM, Campbell, Lance wrote:
>
> PostgreSQL 10.x
>
> What is the best way to restrict the values on a text field to make sure
> they only contain particular values:  Example:  The field “type” can only
> contain the values of “X”, “Y” and “Z”. Would a trigger be the best
> strategy?  Or is there a special SQL type I should use in this particular
> case?
>

Use either a CHECK constraint or FOREIGN KEY.

For just a few items*, *understanding that you must drop and recreate the
constraint to modify it.
http://www.postgresqltutorial.com/postgresql-check-constraint/
CREATE TABLE foo
(
    bar VARCHAR(20) CHECK (bar IN ('X', 'Y', 'Z'))
);

For more items, and simpler additions:
http://www.postgresqltutorial.com/postgresql-foreign-key/

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