В отчете SSRS отображается ошибка параметра "P ID" отсутствует значение

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In SSRS report,I am using total 4 parameters,Parameter "P ID" value is retrieved from parameter "T ID",similarly parameter "R ID" value is retrieved from parameter "P ID".
Case 1:
I Selected only "T ID" then
If parameter "R ID" & "P ID" both having data for particular "T ID",then retrieves data & display report.

Case 2:
I Selected only "T ID" then
If parameter "R ID" & "P ID" both don't have data for particular "T ID",then shows error as
"Parameter "P ID" is missing a value"

Что я уже пробовал:

In parameter dataset ,I have added default "null" value for both "P ID" & "T ID" parameters & also in their dataset.

select R.name,R.id from request R,distribution P
where P.requestdetail =R.gems_id
and P.gems_distributionId=@PlacementID
union 
select null,null


Above working for case 2 only,but actually I want automatic selection of Id,after selecting "T ID",I want "P ID" & "R ID".
Please suggest

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