转自：https://www.cnblogs.com/duhuo/p/5650876.html

mysql格式化日期

mysql查询记录如果有时间戳字段时，查看结果不方便，不能即时看到时间戳代表的含义，现提供mysql格式换时间函数，可以方便的看到格式化后的时间。

1. DATE_FORMAT() 函数用于以不同的格式显示日期/时间数据。

DATE_FORMAT(date,format) 

format参数的格式有

例子：

DATE_FORMAT(NOW(),‘%b %d %Y %h:%i %p‘)
DATE_FORMAT(NOW(),‘%m-%d-%Y‘)
DATE_FORMAT(NOW(),‘%d %b %y‘)
DATE_FORMAT(NOW(),‘%d %b %Y %T:%f‘) 

输出结果：

Dec 29 2008 11:45 PM
12-29-2008
29 Dec 08
29 Dec 2008 16:25:46 

2. MySQL 格式化函数 FROM_UNIXTIME()

SELECT FROM_UNIXTIME(date, ‘%Y-%c-%d %h:%i:%s‘ ) as post_date ,
date_format(NOW(), ‘%Y-%c-%d %h:%i:%s‘ ) as post_date_gmt
FROM `article`  where outkey = ‘Y‘ 

1、FROM_UNIXTIME( unix_timestamp )

　　参数：一般为10位的时间戳，如:1417363200

　　返回值：有两种，可能是类似 ‘YYYY-MM-DD HH:MM:SS‘ 这样的字符串，也有可能是类似于 YYYYMMDDHHMMSS.uuuuuu 这样的数字，具体返回什么取决于该函数被调用的形式。

mysql> select FROM_UNIXTIME(1344887103);
+---------------------------+
| FROM_UNIXTIME(1344887103) |
+---------------------------+
| 2012-08-14 03:45:03       |
+---------------------------+
1 row in set (0.00 sec) 

2、FROM_UNIXTIME( unix_timestamp ，format ) 
　　参数 unix_timestamp ：与方法 FROM_UNIXTIME( unix_timestamp ) 中的参数含义一样； 
　　参数 format : 转换之后的时间字符串显示的格式; 
　　返回值：按照指定的时间格式显示的字符串；

mysql> select FROM_UNIXTIME(1344887103,‘%Y-%M-%D %h:%i:%s‘);
+-----------------------------------------------+
| FROM_UNIXTIME(1344887103,‘%Y-%M-%D %h:%i:%s‘) |
+-----------------------------------------------+
| 2012-August-14th 03:45:03                     |
+-----------------------------------------------+
1 row in set (0.00 sec)
mysql> select FROM_UNIXTIME(1344887103,‘%Y-%m-%D %h:%i:%s‘);
+-----------------------------------------------+
| FROM_UNIXTIME(1344887103,‘%Y-%m-%D %h:%i:%s‘) |
+-----------------------------------------------+
| 2012-08-14th 03:45:03                         |
+-----------------------------------------------+  

1 row in set (0.00 sec) 

3、判断是不是同一天：

SELECT tbl_gamedata.GameMapName,tbl_playerdata.GameMode, tbl_gamedata.MatchMode, tbl_playerdata.GameResult, SUM(tbl_playerdata.GameIsWin) AS tday_winCount,
          SUM(tbl_playerdata.AssistCount) AS tday_assistCount,SUM(tbl_playerdata.KillCount) AS tday_killCount,
          SUM(tbl_player_title.ThreeKill) AS tday_threeKill,SUM(tbl_player_title.FourKill) AS tday_fourKill,SUM(tbl_player_title.FiveKill) AS tday_fiveKill
   FROM tbl_playerdata
     LEFT JOIN tbl_gamedata ON tbl_playerdata.GameID = tbl_gamedata.GameID
     LEFT JOIN tbl_player_title ON tbl_player_title.GameID = tbl_playerdata.GameID AND tbl_player_title.PlayerID = tbl_playerdata.PlayerID
   WHERE tbl_playerdata.PlayerID = user_id AND (tbl_playerdata.GameResult = 2 OR tbl_playerdata.GameResult = 3) AND TO_DAYS(FROM_UNIXTIME(tbl_playerdata.GameStartTime)) = TO_DAYS(NOW())
   GROUP BY tbl_gamedata.GameMapName, tbl_playerdata.GameMode,tbl_gamedata.MatchMode,tbl_playerdata.GameResult;

其中TO_DAYS(FROM_UNIXTIME(tbl_playerdata.GameStartTime)) = TO_DAYS(NOW()) 就是我们需要的判断