Question

For example, I have a column > shopping_cart.status; and this column status should for each record contain one of three values > “incomplete” “complete” or “shipped”. My question is, should it be my application that makes sure that these are the only values used, or do i need to build this into the domain of this attribute on the database side?

Answer 1

Use enums thats exactly what they are meant for.

An ENUM is a string object with a value chosen from a list of
permitted values that are enumerated explicitly in the column
specification at table creation time.

An enumeration value must be a quoted string literal; it may not be an
expression, even one that evaluates to a string value. For example,
you can create a table with an ENUM column like this:

CREATE TABLE shoppingcards (
    shoppingcardstatus ENUM('incomplete', 'complete', 'shipped')
);

see: http://dev.mysql.com/doc/refman/5.0/en/enum.html