Ahmed,
I had this issue and solved it this way.
I created a check box field in TB
You need good business process rules to make sure that the check box is set for the "one special TB" for TA only.
Then you can create a Summary field TA for the MAX RID in TB where the CB is True
You now have the Record ID in TB for the Special TB
Your second step above is still requried but you set the Reference Field in the relationship to that Summary Field and you will get a single result.
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Don Larson
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