A combine join combines like records from a single data source. Combine is a pseudo-join that operates on a single source.
In the example below, there are multiple records with Id=A, Id=C, and Id=D. These records are combined. Only one records exists for Id=B and Id=E, so neither of these records is combined, but both are processed and included in the joined data.
Note: Combining large numbers of records will cause Forge to print warning messages about slow performance.
