With that qry I have this result and its not the expected.

SampleID|ClassID|ResultID|TestID

___A____|___X__|___R1___|___1____

___A____|___X__|___R2___|___4____

___A____|___Y__|___R1___|___1____

___A____|___Y__|___R2___|___4____

___A____|___Z__|___R1___|___1____

___A____|___Z__|___R2___|___4____

I want this

SampleID|ClassID|ResultID|TestID

___A____|___X___|___R1___|___1____

___A____|___Y___|___R2___|___4____

___A____|___Z___|__NULL__|__NULL__

Thank you