If you are running your transformation on the Pentaho engine, use the following instructions to set up the Merge rows (diff) step.
Important: When using the Pentaho transformation engine, the reference
rows and compare rows must be sorted on the specified keys. When using the Merge rows (diff) step within a
PDI
transformation, such as with the Sort rows step, sorting works correctly. However, if the
data is sorted outside of PDI, such as in a SQL query, you may run into issues with the internal case
sensitive/insensitive flag or other collations. If you are using the Merge rows (diff) step with the Spark engine, see Using Merge rows (diff) on the Spark engine.