How to do subtraction in mysql

I want to subtract 1 from a variable that is stored in my table in mysql

I am doing it for this request

UPDATE table SET  var = var -1

      

        
        
        
      

    

but when i do it

0 - 1 = -1

      

        
        
        
      

    

but mysql do

0 - 1 = 9223372036854775807

when i set to bigint when i set it to int property then it does

0 -1 = 2147483647

      

        
        
        
      

    

what i do to get

0 - 1 = -1