All Time Show Null value
Please help me what is the wrong in my code

declare @mxdbvlu  int
 declare @dbvlunm int
  set @mxdbvlu= (select max(Database_name) from TBL_FY_SELECT_1)
 if @mxdbvlu = null 
 set @dbvlunm=1000
 else 
 set @dbvlunm=sum(@mxdbvlu+1)
  select @dbvlunm,@mxdbvlu

Hopefully in line 4. if @mxdbvlu == null instead of if @mxdbvlu = null