Обсуждение: How to restrict

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? 

Easy with a CHECK CONSTRAINT, like :
create table baba (type varchar(10) CHECK (type in ('X','Y','Z')));

 

Thanks,

 

LANCE CAMPBELL

Software Architect

 

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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/