I previously wrote about using SQL check constraints in MySQL. It seems however that the MySQL relational database management system (RDBMS) does not actually support the fundamental verification used by check constraints in other RDBMSs. This means that although you can add check constraints to tables without issue, they are not validated and data is [...]

An SQL check constraint is used and designed in the schema of a database table to restrict the range of values that can be entered into a specific field. In many experienced, they are very rarely used. However, these simple checks, entered at the time of database table creation, can provide additional safe guards against [...]