database - SSRS Blank Parameters -

i have 3 simple parameters, text, , allow multiple values blank values. there no available values or default values, want users type value themselves. when leaving parameters blank, no data shown, because there no blank values. however, want show data when there no value entered parameter. how can this?

this query looks right now

select  [programno]       ,[acctno]       ,[claimno]       ,[totalcharges]       ,[totalpayment]       ,[type]   dataline programno in (@programno)   , acctno in (@acctno)   , claimno in (@claimno) 

you can add or allow null (or blank) value each condition - depending on have allowed in parameter.

where (programno in (@programno) or @programno null)   , (acctno in (@acctno) or @acctno null)   , (claimno in (@claimno) or @claimno null) 

or if allow blank values instead:

where (programno in (@programno) or @programno = '' )   , (acctno in (@acctno) or @acctno = '' )   , (claimno in (@claimno) or @claimno = '' )