数据如下：
id date fromId toId
--------------------------------------
1 2013-01-01 1 2
2 2013-01-02 2 1
3 2013-01-03 1 3
4 2013-01-04 3 1
5 2013-01-05 4 1
6 2013-01-06 1 4
如何才能查询出fromId或toId包含某个值，但fromId和toId不相互重复的数据？ 例如，查询fromId或toId包含1，去除fromId和toId中数据互换的列，仅取日期最大的值，查询结果为：
id date fromId toId
--------------------------------------
2 2013-01-02 2 1
4 2013-01-04 3 1
6 2013-01-06 1 4
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SELECT max(`date`),maxId,minId FROM (SELECT `date`,IF(fromId>toId,fromId,toId) AS maxId,IF(fromId>toId,toId,fromId) AS minId FROM `table`) AS `tmp` GROUP BY maxId,minId
select distinct fromId,* from table group by toId;