understanding sql functions

You can try this function

create function Check_Issue()
 returns  int
   As
     begin
      Declare @count int
      Declare @result int
        select @count = count(issue) from project   --take value in one variable
           if (@count = 0 )                          -- check in if loop
            Begin
              set  @result = 1
            End
            else if (@Count > 0 and @count < 5)
              set  @result = 0
            else
              set  @result = -1
       return @result                               -- return value
   End