建立資料庫db12

create database db12 charset=utf8;
use db12;

準備表和記錄

CREATE TABLE blog (
    id INT PRIMARY KEY auto_increment,
    NAME CHAR (32),
    sub_time datetime
);

插入記錄

INSERT INTO blog (NAME, sub_time)
VALUES
    ('第1篇','2015-03-01 11:31:21'),
    ('
 
第2篇','2015-03-11 16:31:21'),
    ('第3篇','2016-07-01 10:21:31'),
    ('第4篇','2016-07-22 09:23:21'),
    ('第5篇','2016-07-23 10:11:11'),
    ('第6篇','2016-07-25 11:21:31'),
    ('第7篇','2017-03-01 15:33:21'),
    ('第8篇','2017-03-01 17:32:21'),
    ('第9篇','2017-03-01 18:31:21');

提取sub_time欄位的值，按照格式後的結果即"年月"來分組

mysql>
 
 select date_format(sub_time,'%Y-%m'),count(id) from blog group by date_format(sub_time,'%Y-%m');
+-------------------------------+-----------+
| date_format(sub_time,'%Y-%m') | count(id) |
+-------------------------------+-----------+
| 2015-03                       |         2 |
| 2016-07                       |
 
         4 |
| 2017-03                       |         3 |
+-------------------------------+-----------+
3 rows in set (0.00 sec)