kamlesh_vaghela, thanks for the input, thanks to you I have it working. But SourceA is not needed where it is. #2 SourceC is listed twice, and the 2nd time should be SourceA if it is removed from the beginning.
The working command looks like this: [ search SourceB | dedup field1
| fields field1]
[ search SourceB | dedup field1 | fields field1]
| join field1
[ search SourceA | dedup field1 | fields field1]
| table field1 | dedup field1