Show blank data when no new data exists

Hello,

I have a matrix visualization with a single column for every day (pulled from table A).   I have a second table, table B, which only has data for some days.  When I display the data from table B in the matrix, where there is no data, the data is simply duplicated from the last time there is data.   How do I turn this off so that it'll be blank if there's no data?

Thanks.