请教一句sql语句？

[chancehi]

id name num
-------------------------
1 aaa 123456
2 bbb 123456
3 ccc 23412
4 aaa 789
5 ccc 5445
6 bbb 12367
.. ... ....
如果我想要将name为aaa，并且id为最大值的行中，将num值改为756
应如何写

[hitexam]

update chancehi a ,(select id from chancehi where name='aaa' order by id desc limit 1 ) b set a.num=756 where a.id=b.id;

[chancehi]

[Quote=引用 1 楼 hitexam 的回复:]
update chancehi a ,(select id from chancehi where name='aaa' order by id desc limit 1 ) b set a.num=756 where a.id=b.id;
[/Quote]
谢谢