一. 日期与时间戳
数据库日期写入大多数用的是时间戳格式，我们在查询的时候可能不是很方便
mysql提供了两个函数:

  1. from_unixtime(time_stamp) -> 将时间戳转换为日期 
    mysql> select from_unixtime(create_time) from tag limit 10;
+----------------------------+
| from_unixtime(create_time) |
+----------------------------+
| 2017-03-15 08:30:46        |
| 2017-03-15 10:30:06        |
| 2017-03-14 17:06:42        |
| 2017-03-12 09:31:31        |
| 2017-03-15 05:08:37        |
| 2017-03-05 06:54:21        |
| 2017-03-14 17:18:20        |
| 2017-03-15 09:01:26        |
| 2017-03-01 02:37:46        |
| 2017-02-28 05:02:27        |
+----------------------------+
10 rows in set (0.00 sec)
  2. unix_timestamp(date) -> 将指定的日期或者日期字符串转换为时间戳 
    select * from tag  where create_time >= unix_timestamp('2018-10-26 00:00:01') and create_time <= unix_timestamp('2018-12-11 23:59:59') order by total  desc limit 10;

二. 查询近30天的数据
SELECT * FROM 表名 where DATE_SUB(CURDATE(), INTERVAL 30 DAY) <= date(时间字段名)

mysql> select * from tag where date_sub(curdate(),interval 45 day) <= from_unixtime(create_time) order by total desc limit 10;

mysql查询今天、昨天、7天、近30天、本月、上一月 数据：
https://www.cnblogs.com/qinweizhi/p/5918048.html