# limit 50
select * from tb order by created_at desc limit 50 offset 0;
select * from tb order by created_at desc limit 50 offset 50;
select * from tb order by created_at desc limit 50 offset 100;
select * from tb order by created_at desc limit 50 offset 150;
select * from tb order by created_at desc limit 50 offset 200;
# limit 100
select * from tb order by created_at desc limit 100 offset 100;
select * from tb order by created_at desc limit 200 offset 200;
这里遇到一个问题limit 50 和limit 100 取出的数据不一致、而且limit 50 offset xx 会取出原来重复的数据
解决办法
在order by created_at desc 后面加一个带顺序的索引例如id
select * from tb order by created_at desc , id desc limit 50 offset 0;
具体原因【待证实】：
目前猜测是mysql 取出对应limit的数据后进行排序，由于created_at是秒单位，所以在同一时刻会有很多数据，mysql每次进行排序的时候就可能会出现重复的状况
