mysql 根据时间戳按年月日分组统计

#按月统计购买的人数(而且去掉重复的人数)
SELECT DATE_FORMAT(createday,'%Y%m') months,COUNT(DISTINCT uid) uids FROM principal
WHERE `type`=1 AND parentid IS NULL
GROUP BY months

#按周来统计
SELECT DATE_FORMAT(createday,'%Y%u') weeks,COUNT(DISTINCT uid) uids FROM principal
WHERE `type`=1
GROUP BY weeks;

#按照天来统计
SELECT DATE_FORMAT(createday,'%Y%m%d') days,COUNT(DISTINCT uid) uids  FROM principal
WHERE `type`=1
GROUP BY days;