To fetch highest row in table

SELECT * FROM `bids` as b where
amount = (select max( amount) from bids where userid = b.userid) and
timestamp = (select max( timestamp) from bids where userid = b.userid)
group by userid

For examples

id userid timestamp amount
1 101     1122334  223
2 102     1222334  323
3 101     1322334  523
4 102     1522334  723
5 101     1622334  283
6 102     1722334  293
7 102     1822334  233
8 102     2222334  203




id userid timestamp amount
1 101      1622334 283
2 102      2222334 203