New and old ways to emulate CHECK constraints, DOMAIN

Correctness of data comes in different forms. One is referential integrity, also known as foreign keys. Another is CHECK constraints. While MySQL supports foreign keys, it doesn’t support CHECK constraints. Today we will look at three ways to emulate them:

• triggers
• views
• generated columns (new in MySQL 5.7)

This is also relevant to another SQL feature: DOMAIN, which, in short, is a user-defined type composed of a base type (INT, CHAR, …), a default value, and a constraint on acceptable values – the latter being some simple sort of CHECK constraint.…

Source: mysqlserverteam.com