confused by mysql command:select * ..order by if(death is null,0,1),death;

i am learning mysql command to retrieve information from a table.and i want to sort the result.i have a table named president,contains fields like:first_name,last_name,death(which can be null to indicate the president is still alive or a death-date ),so i use :
select first_name,last_name,death from president order by if(death is null,0,1),death desc;
the result is like(of the death field):
null
null
null
2004-06-05
1994-04-22
...
...
the result confused me.
since it's ordered by two fields at the same time:one field can be 0 or 1,the other is a date field,so things is much like the following:
0,null
0,null
0,null
1,2004-06-05
1,1994-04-22
...
but it's by desc order ,i think the result should be:
[1,]2004-06-05
[1,]1994-04-22
[0,]null
[0,]null
[0,]null
but it not .who can tell me why?






lanxiazhi
2006-08-03