MySQL按天，按周，按月，按时间段统计【转载】

select DATE_FORMAT(create_time,"%Y%m%d") days,count(caseid) count from tc_case group by days;
select DATE_FORMAT(create_time,"%Y%u") weeks,count(caseid) count from tc_case group by weeks;
select DATE_FORMAT(create_time,"%Y%m") months,count(caseid) count from tc_case group by months;