Datatypes in Join Columns

The columns being joined must have the same or compatible datatypes. Use the convert function when comparing columns that are assigned datatypes that cannot be implicitly converted. Columns being joined need not have the same name, although they often do.

If the datatypes used in the join are compatible, SAP ASE automatically converts them. For example, SAP ASE converts among any of the numeric type columns:
Among any of the character type and date columns, SAP ASE converts:
Related concepts
Transact-SQL Functions