Pattern for idempotent sql alter scripts using temporary stored procedures to implement conditional logic.

idempotentAlter.sql

delimiter //

drop procedure if exists trySomething//
create procedure trySomething(in _param1 int, in _param2 int)
begin  
  -- Condition could be a count, a boolean, whatever. In this case assuming might be running a "select count(*)"
  -- to determine if a certain row has already been inserted.
  declare _condition int default null;
  set _condition = (<SOME_SELECT_THAT_SIGNIFIES_IF_YOUVE_ALREADY_RUN_THIS_SCRIPT>);

  if _condition = 0 then
    select 'have not run before, doing the work';

    -- your code here
  else
    select 'nothing to do, been here before';
  end if;
end//

delimiter ;

call trySomething(<importantParam1>, <importantParam2>);

-- cleanup temp proc(s)
drop procedure if exists trySomething;