Join columns require like data types for optimal performance. Sybase IQ allows you to make an ad hoc join on any data types for which an implicit conversion exists. Unless join column data types are identical, however, performance can suffer to varying degrees, depending on the data types and the size of the tables. For example, while you can join an INT to a BIGINT column, this join prevents certain types of optimizations. The IQ index advisor identifies performance concerns for join columns whose data types differ.
For tables of implicit data type conversions, see Chapter 7, “Moving Data In and Out of Databases” in Sybase IQ System Administration Guide.
