SSRS LOOKUP with row grouping

Question

I am trying to add a column to tablix that uses different dataset. Now the dataset1 holds new data and dataset2 holds old comparison data.

The tablix is using dataset1 and the row in question is grouped by D_ID now I added a column that needs to binded with D_ID(dataset1) to D_ID(dataset2)

=-1*sum(Lookup(Fields!D_ID.Value, Fields!D_ID.Value, Fields!BUD_OLD.Value, "OLD")+Lookup(Fields!D_ID.Value, Fields!D_ID.Value, Fields!ACK_BUD_OLD.Value, "OLD"))

However this does take into account that what I need is all the rows from BUD_OLD with D_ID = smth to be summed together. The lookup only returns one value not a sum of all values with D_ID.

Example

D_ID        SUM(BUD_NEW+ACK_BUD_NEW)           SUM(BUD_OLD+ACK_BUD_OLD)         
**100**           **75**  (40+35)                    **15**(SHOULD BE 15+20=35) 

How can I get the sum?

Answer 1

LOOKUP only gets a single value.

You would need to use LOOKUPSET and a special function to SUM the results.

Luckily, this has been done before.

SSRS Groups, Aggregated Group after detailed ones

From BIDS:

LOOKUP : Use Lookup to retrieve the value from the specified dataset for a name-value pair where there is a 1-to-1 relationship. For example, for an ID field in a table, you can use Lookup to retrieve the corresponding Name field from a dataset that is not bound to the data region.

LOOKUPSET : Use LookupSet to retrieve a set of values from the specified dataset for a name-value pair where there is a 1-to-many relationship. For example, for a customer identifier in a table, you can use LookupSet to retrieve all the associated phone numbers for that customer from a dataset that is not bound to the data region.

Answer 2

Your expression requires a second "sum"

Try the following:

-1*sum(Lookup(Fields!D_ID.Value, Fields!D_ID.Value, Fields!BUD_OLD.Value, "OLD")+SUM(Lookup(Fields!D_ID.Value, Fields!D_ID.Value, Fields!ACK_BUD_OLD.Value, "OLD")