Postgres ENUM data type or CHECK CONSTRAINT?

Question

I have been migrating a MySQL db to Pg (9.1), and have been emulating MySQL ENUM data types by creating a new data type in Pg, and then using that as the column definition. My q

Answer 1

As other answers point out, check constraints have flexibility issues, but setting a foreign key on an integer id requires joining during lookups. Why not just use the allowed values as natural keys in the reference table?

To adapt the schema from punkish's answer:

CREATE TABLE valid_colors (
    color TEXT PRIMARY KEY
);

INSERT INTO valid_colors (color) VALUES 
    ('red'),
    ('green'),
    ('blue');

CREATE TABLE t (
    color TEXT REFERENCES valid_colors (color) ON UPDATE CASCADE
);

Values are stored inline as in the check constraint case, so there are no joins, but new valid value options can be easily added and existing values instances can be updated via ON UPDATE CASCADE (e.g. if it's decided "red" should actually be "Red", update valid_colors accordingly and the change propagates automatically).