"Cannot generate query no valid fields projected from the Source Qualifier" generating a SQL Override in a Source Qualifier

Problem Description

After clicking on the Generate SQL button in a SQL override the following error is encountered: Cannot generate query because there are no valid fields projected from the source qualifier

Solution

The output ports of the Source Qualifier must be connected to another transformation in the mapping. Only the ports that are connected to another transformation will be included in the SELECT clause of the SQL that is generated. To resolve do the following: Close the SQL Override window. Connect the ports from the Source Qualifier to the next transformation in the mapping. Create the SQL Override.