So it's possible to store "2" into a boolean column in MySQL?
Yes. *.frm files doesn't store type as "BOOLEAN" at all. Only as TINYINT(1). So, this isn't really a type, but actually a synonym for TINYINT(1). I'll first have to read into type domains for MySQL Sorry for introducing a confusion, but MySQL doesn't support them yet. But, for example, Postgres does: http://developer.postgresql.org/pgdocs/postgres/sql-createdomain.html There is also CREATE TYPE in MSSQL for the same purpose.
