How can I check a column in oracle which is black and datatype is NUMBER : I have a table which name is HARDWARE_ISSUE . it has two column div_code and branch code . Datatype of div_code is NUMBER and branch_code is varchar2. I want to select branch_code when the value of div_code is blank. My query is below:
        
    select  (case when div_code= null then  to_char(branch_code) else to_char(div_code) end) as brordiv  from HARDWARE_ISSUE
 
But It could not select branch_code when div_code is empty. I also run the query below: 
    
       select * from HARDWARE_ISSUE where div_code= null

It also not produce any row. but there 15 rows which contain empty div_code. I am using oracle 11g. Please help me.

 