MySQL Workbench Release Notes
Most ODBC compliant databases may be migrated using the generic database support. In this case, code objects will not be retrieved from the source database; only tables and data.
When using the generic support, column data types are mapped using the following steps:
It searches for the first entry in the for the source type name. If the length/scale ranges of the entry matches the source column, it will pick that type. Otherwise, it continues searching.
If no matches were found in the generic table, then it tries to directly map the source type to a MySQL type of the same name.
If the source type name doesn't match any of the MySQL data types, then it is not converted and an error is logged. From here you can specify the target datatype in the Manual Object Editing step of the wizard.