The schema defined through tCombinedSQLInput can be different from that of the source table as you can just instantiate the desired columns of the source table. Therefore, tCombinedSQLInput also plays a role of column filtering.
In this scenario, the source database table has seven columns: id, first_name, last_name, city, state, date_of_birth, and salary while tCombinedSQLInput only instantiates four columns that are needed for the aggregation: id, state, date_of_birth, and salary from the source table.
