Hi,
try creating a query returning just [Transaction hours], merge your original query with this query on [Transaction hours]. Bring the merged [Transaction hour] in your table. Create a measure variable [new data] = If(IsNull([data]);0;[data]). Bringing the merged [Transaction hour] and [new data] on a table will do the trick.
If you need other dimensions from your original query, bring them onto the table as well and then follow Pavan's advice.
Cheers,
Rogerio