1、统计某一个月

SELECT * FROM 表名 WHERE PERIOD_DIFF( date_format( now( ) , '%Y%m' ) , date_format( 时间字段名, '%Y%m' ) ) =1  #当前月份统计

SELECT * FROM 表名 WHERE DATE_FORMAT( 时间字段名, '%Y%m' ) = DATE_FORMAT( CURDATE( ) , '%Y%m' )                #某月统计

2、按月份聚合统计

SELECT count(*) as '注册量',DATE_FORMAT(created_time,'%Y-%m') as '月份'  FROM user GROUP BY DATE_FORMAT(created_time,'%Y-%m');  
SELECT count(*) as '报单量',DATE_FORMAT(created_time,'%Y-%m') as '月份'  FROM loan GROUP BY DATE_FORMAT(created_time,'%Y-%m');