This constraint is automatically included for types using the JSON alias from MariaDB 10.4.3. In order to ensure that a a valid json document is inserted, the JSON_VALID function can be used as a CHECK constraint. MariaDB implements this as a LONGTEXT rather, as the JSON data type contradicts the SQL standard, and MariaDB's benchmarks indicate that performance is at least equivalent. JSON is an alias for LONGTEXT introduced for compatibility reasons with MySQL's JSON data type. Differences Between MySQL JSON Strings and MariaDB JSON Strings.Converting a MySQL TABLE with JSON Fields to MariaDB.Replicating JSON Data Between MySQL and MariaDB.