Hope you are doing good!
I agree with Arul. You can make use of if(isnull(dimension),'0',dimension)
However, if you are loading data from ODBC source then use, SET NULLDISPLAY='0'; This will substitute all NULL values from the ODBC data source on the lowest level of data input. This will save efforts for writing validation check at every place.
NOTE: The use of NULLDISPLAY only affects data from an ODBC data source.