語法：
DATE_FORMAT(date,format)
date 參數是合法的日期。format 規定日期/時間的輸出格式。
DATE_FORMAT實例
1.把字符串轉爲日期格式
實例：
SELECT DATE_FORMAT(‘2017-09-20 08:30:45’, ‘%Y-%m-%d %H:%i:%S’);
輸出結果：
2017-09-20 08:30:45（日期Date格式）
2.把日期轉爲字符串格式
實例：
SELECT DATE_FORMAT(NOW(), ‘%Y-%m-%d %H:%i:%S’);
2017-04-05 16:53:59（String型格式）
按年彙總，統計
SELECT sum(mymoney) as totalmoney, count(*) as sheets FROM mytable
GROUP BY date_format(col, '%Y');
按月彙總，統計
SELECT sum(mymoney) as totalmoney, count(*) as sheets FROM mytable
GROUP BY date_format(col, '%Y-%m');
按季度彙總，統計
SELECT sum(mymoney) as totalmoney,count(*) as sheets FROM mytable
GROUP BY concat(date_format(col, '%Y'),FLOOR((date_format(col, '%m')+2)/3));
按天統計數據
數據庫中的日期爲精確到秒的，想按照天統計，每一天的數據，sql語句如下
原有的查詢出來的結果是每天每小時每秒的數據統計
SELECT read_time,sum(read_number) as read_total FROM `mdz_activity_share` where ai_id=340 and read_number > 0 GROUP BY
read_time asc
優化後：
SELECT date_format(read_time, '%Y-%m-%d'),sum(read_number) as read_total FROM `mdz_activity_share` where ai_id=340 and read_number > 0 GROUP BY date_format(read_time, '%Y-%m-%d') asc
按小時統計
SELECT sum(mymoney) as totalmoney,count(*) as sheets FROM mytable
GROUP BY date_format(col, '%Y-%m-%d %H ');
查詢 本年度的數據:
SELECT * FROM mytable WHERE year(FROM_UNIXTIME(my_time)) = year(curdate())
查詢數據附帶季度數:
SELECT id, quarter(FROM_UNIXTIME(my_time)) FROM mytable;
查詢 本季度的數據:
SELECT * FROM mytable WHERE quarter(FROM_UNIXTIME(my_time)) = quarter(curdate());
查詢 本月統計:
SELECT * FROM mytable
where month(my_time1) = month(curdate()) and year(my_time2) = year(curdate())
查詢 本週統計:
SELECT * FROM mytable
where month(my_time1) = month(curdate()) and week(my_time2) = week(curdate())
查詢 N天內記錄:
WHERE TO_DAYS(NOW())-TO_DAYS(時間字段)<=N