multivalued parameters in SSRS - selecting only one value

Question

I've set up a report with a multi-valued parameter. The dataset is essentially

select 'Abc' as field1
Union all
select 'lmnop'
union all
select 'xyz'
order by Field1

Available values - Label and Value are both set to Field1 Default values - Value is set to Field1

I would expect only the 'Abc' to be selected by default and the rest unselected. But instead, I'm seeing all of them selected. This works as expected with single valued parameters.

SSRS 2008 R2

Answer 1

Based on this answer and some quick testing, it seems that when a parameter is defined as multi-value and there is no NULL in the dataset, the default behaviour is to select all of them. Otherwise, it selects None. Select All as default value for Multivalue parameter

Which makes sense, I suppose, from a behaviour perspective. You're allowing multi-select so why not assume someone will start with everything selected? Seems as arbitrary as expecting the first thing to be selected.

Answer 2

Got it, whatever is returned from the default values dataset will become selected when the report is run.

So if I have as Dataset for Available option

select 'a' as field1
union all
select 'b'
union all
select 'c'

and I have as Dataset2 for Default option

Select 'b' as selectedField

Then, only 'B' will be selected by default when the report is run. Makes sense.