mysql 根據時間戳按年月日分組統計

#按月統計購買的人數(而且去掉重複的人數)
SELECT DATE_FORMAT(createday,'%Y%m') months,COUNT(DISTINCT uid) uids FROM principal
WHERE `type`=1 AND parentid IS NULL
GROUP BY months

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

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