example1：

-- 判断两个时间差大于4个小时

select timestamp '2013-11-11 10:00:00' - timestamp '2013-11-08 12:00:00' > interval '4 hour';

example2：

-- 获取时间差的总体小时差 然后再判断

mrapp=> select extract(day from t) * 24 + extract(hour from t) > 4 from (select (timestamp '2013-12-14 12:00:00' - timestamp '2013-12-11 4:00:00') as t) as a;

其他的都比较麻烦了 暂不列