mysql使用FROM_UNIXTIME将时间戳按日期group by

1.功能

将Unix时间戳转换成指定或默认的日期字符串官宣。
它具有的特点

1. 使用整型的高效存储和查询时间（时间戳）
2. 使用此函数兼容日期的时间处理（可读性）

2. 语法

FROM_UNIXTIME(unix_timestamp[,format])
即：省略格式化字符串和指定格式化字符串，两种方式
FROM_UNIXTIME(unix_timestamp)
FROM_UNIXTIME(unix_timestamp,format)

铁路图如下：

3.使用

比如按照小时汇总数据

select FROM_UNIXTIME(ReportTime, '%H'), sum(Value) from reporter_data group by FROM_UNIXTIME(ReportTime, '%H');

+---------------------------------+------------+
| FROM_UNIXTIME(ReportTime, '%H') | sum(Value) |
+---------------------------------+------------+
| 00                              |          0 |
| 01                              |          2 |
| 02                              |          4 |
| 03                              |          6 |
| 04                              |          8 |
| 05                              |         10 |
| 06                              |         12 |
| 07                              |         14 |
+---------------------------------+------------+
8 rows in set (0.00 sec)

常用的格式控制比如：’%Y-%m-%d %H:%i:%s’。然而这些并不容易记住，一种捷径就是结合使用get_format,它可以通过显示DATE, DATETIME, TIME和指定的标准获得所需的日期时间格式控制字符串，比如

MySQL [coding]> select FROM_UNIXTIME(ReportTime, GET_FORMAT(DATE, 'ISO')), sum(Value) from device_data group by FROM_UNIXTIME(ReportTime, GET_FORMAT(DATE, 'ISO'));
+----------------------------------------------------+------------+
| FROM_UNIXTIME(ReportTime, GET_FORMAT(DATE, 'ISO')) | sum(Value) |
+----------------------------------------------------+------------+
| 2019-11-29                                         |         56 |
+----------------------------------------------------+------------+

更是格式控制字符串如下：

Specifier	Description
%a	Abbreviated weekday name (Sun…Sat)
%b	Abbreviated month name (Jan…Dec)
%c	Month, numeric (0…12)
%D	Day of the month with English suffix (0th, 1st, 2nd, 3rd, …)
%d	Day of the month, numeric (00…31)
%e	Day of the month, numeric (0…31)
%f	Microseconds (000000…999999)
%H	Hour (00…23)
%h	Hour (01…12)
%I	Hour (01…12)
%i	Minutes, numeric (00…59)
%j	Day of year (001…366)
%k	Hour (0…23)
%l	Hour (1…12)
%M	Month name (January…December)
%m	Month, numeric (00…12)
%p	AM or PM
%r	Time, 12-hour (hh:mm:ss followed by AM or PM)
%S	Seconds (00…59)
%s	Seconds (00…59)
%T	Time, 24-hour (hh:mm:ss)
%U	Week (00…53), where Sunday is the first day of the week; WEEK() mode 0
%u	Week (00…53), where Monday is the first day of the week; WEEK() mode 1
%V	Week (01…53), where Sunday is the first day of the week; WEEK() mode 2; used with
%v	Week (01…53), where Monday is the first day of the week; WEEK() mode 3; used with
%W	Weekday name (Sunday…Saturday)
%w	Day of the week (0=Sunday…6=Saturday)
%X	Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V
%x	Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v
%Y	Year, numeric, four digits
%y	Year, numeric (two digits)
%%	A literal % character
%x	x, for any “x” not listed above