title: Blank Parameter to Null Parameter in SSRS
body: <p>I have a drilldown report whose parameters are: parent report - @valid Nvarchar(20) = '' and in child report - @valid Nvarchar(20) = Null. </p>
  
  <p>Both reports run very well but I have an issue after mapping up this parameters in the Text Box Properties > Action > Go to Report. When the report is run I get the error, </p>
  
  <p>"the value provided for the report parameter is not valid"</p>
  
  <p>The query for this report is from a stored Procedure. In the child report, Parameter Properties, I have ticked the "allow Null values" text box, Set available parameter to come from a query and specify a default value to come from a query. What have I done wrong to allow for the error returned? Your help is appreciated.</p>
  
  <p>Thank you.</p>