MySQL Subquery Problem

[Matt]

Here is a database created for the purpose of this SUBJECT:

CREATE TABLE `user_info` (
`id` int(7) NOT NULL auto_increment,
`name` varchar(40) NOT NULL default '',
`ip` varchar(15) NOT NULL default '',
`opp_name` varchar(40) NOT NULL default '',
`opp_ip` varchar(15) NOT NULL default '',
`play` tinyint(1) NOT NULL default '0',
`date` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
PRIMARY KEY (`id`)
)

How to form a single/multiple subquery to solve such problems:

1. Delete all users that have the TIMESTAMP older than 1day
2. Exchange values between 2 users, so that User_1st.(name, ip)>>User_2nd.(opp_name, opp_ip) and vice versa than set the value PLAY for both users to 1

PS> Do you think it is possible to make a single/multi subquery solving the problem above? I have resigned and don;t really know what to do with it.