MySql按周，按月，按日分组统计数据

知识关键词：DATE_FORMAT

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

例：查询items_info表中务id为842且时间大于2019-09-01的数据，根据每日的数据量进行排序分组

select count(*),DATE_FORMAT(create_time,'%y-%m-%d')days from items_info where task_id=842 and create_time >"2019-09-01" group by days order by days desc;

根据format字符串格式化date值。下列修饰符可以被用在format字符串中：

• format 可以使用的格式有: