MySql按周，按月，按日分組統計數據

• select DATE_FORMAT(date,'%Y%u') weeks,count(id) count from table group by weeks;  
• select DATE_FORMAT(date,'%Y%m%d') days,count(id) count from table group by days;  
• select DATE_FORMAT(date,'%Y%m') months,count(id) count from table group by months;