If you’ve done any database work at all, you’re no doubt familiar with a “not null” constraint that prevents inserting null into a column of the database.
|||CREATE TABLE people (|
|||id INT NOT NULL,|
|||name VARCHAR(255) NOT NULL,|
|||birthdate DATE NULL|
In this table, id and name may not be NULL, but birthdate may be. Postgres takes the “null constraint” concept much further by allowing arbitrary constraints on fields. Postgres also has support for regular expressions. This means we can create a constraint on our email field that requires its value to match the same regular expression we used in our Rails code. This would prevent non-company email addresses from being inserted ...