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mysql> select name, max(age),grade from  stu group by grade;
ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'hisen.stu.name' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

mysql> SELECT A.* FROM stu A INNER JOIN (SELECT MAX(AGE) AS MAX_AGE,GRADE FROM stu GROUP BY GRADE ) B ON A.GRADE = B.GRADE AND A.AGE= B.MAX_AGE;
+----+------+------+-------+
| id | name | age  | grade |
+----+------+------+-------+
|  3 | c    |   13 |     1 |
|  6 | f    |   13 |     2 |
+----+------+------+-------+
2 rows in set (0.00 sec)

mysql> describe stu;
+-------+---------+------+-----+---------+----------------+
| Field | Type    | Null | Key | Default | Extra          |
+-------+---------+------+-----+---------+----------------+
| id    | int(11) | NO   | PRI | NULL    | auto_increment |
| name  | char(1) | YES  |     | NULL    |                |
| age   | int(11) | YES  |     | NULL    |                |
| grade | int(11) | YES  |     | NULL    |                |
+-------+---------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> select * from stu;
+----+------+------+-------+
| id | name | age  | grade |
+----+------+------+-------+
|  1 | a    |   11 |     1 |
|  2 | b    |   12 |     1 |
|  3 | c    |   13 |     1 |
|  4 | d    |   11 |     2 |
|  5 | e    |   12 |     2 |
|  6 | f    |   13 |     2 |
+----+------+------+-------+
6 rows in set (0.00 sec)

mysql> select max(name), max(age),grade from  stu group by grade;
+-----------+----------+-------+
| max(name) | max(age) | grade |
+-----------+----------+-------+
| c         |       13 |     1 |
| f         |       13 |     2 |
+-----------+----------+-------+
2 rows in set (0.01 sec)

curl -sSL http://acs-public-mirror.oss-cn-hangzhou.aliyuncs.com/docker-engine/internet | sh -

sudo apt-get update
sudo apt-get install \
     linux-image-extra-$(uname -r) \
     linux-image-extra-virtual

sudo apt-get install \
     apt-transport-https \
     ca-certificates \
     curl \
     software-properties-common

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

yourPath\maven-3.3.9\conf\settings.xml

<mirrors>
</mirrors>

<!--阿里云：速度挺快-->
<mirror>
	<id>nexus-aliyun</id>
	<mirrorOf>central</mirrorOf>
	<name>Nexus aliyun</name>
	<url>http://maven.aliyun.com/nexus/content/groups/public</url>
</mirror>

<!--谷歌：北京速度不错-->
<mirror>
  <id>google-maven-central</id>
  <name>Google Maven Central</name>
  <url>https://maven-central.storage.googleapis.com</url>
  <mirrorOf>central</mirrorOf>
</mirror>

select *
  from (select t.*, rownum rn
          from (select * from EW_AUTH_FLOW) t
         where rownum <= 5)
 where rn > 2;

select *
  from (select t.*, rownum rn from ew_auth_flow t where rownum <= 5)
 where rn > 2;

select *
  from (select t.*, rownum rn from ew_auth_flow t)
 where rn between 2 and 5;

sudo vi /etc/redis/redis.conf

bind 127.0.0.1

bind 0.0.0.0

service redis restart

#登陆数据库
hisen@ubuntu:/$ mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.7.17-0ubuntu0.16.04.2 (Ubuntu)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| employees          |
| log4j              |
| mysql              |
| performance_schema |
| ssm                |
| sys                |
+--------------------+
7 rows in set (0.00 sec)

mysql> use employees
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
+----------------------+
| Tables_in_employees  |
+----------------------+
| current_dept_emp     |
| departments          |
| dept_emp             |
| dept_emp_latest_date |
| dept_manager         |
| employees            |
| salaries             |
| titles               |
+----------------------+
8 rows in set (0.00 sec)

mysql> select * from employees limit 10;
+--------+------------+------------+-----------+--------+------------+
| emp_no | birth_date | first_name | last_name | gender | hire_date  |
+--------+------------+------------+-----------+--------+------------+
|  10001 | 1953-09-02 | Georgi     | Facello   | M      | 1986-06-26 |
|  10002 | 1964-06-02 | Bezalel    | Simmel    | F      | 1985-11-21 |
|  10003 | 1959-12-03 | Parto      | Bamford   | M      | 1986-08-28 |
|  10004 | 1954-05-01 | Chirstian  | Koblick   | M      | 1986-12-01 |
|  10005 | 1955-01-21 | Kyoichi    | Maliniak  | M      | 1989-09-12 |
|  10006 | 1953-04-20 | Anneke     | Preusig   | F      | 1989-06-02 |
|  10007 | 1957-05-23 | Tzvetan    | Zielinski | F      | 1989-02-10 |
|  10008 | 1958-02-19 | Saniya     | Kalloufi  | M      | 1994-09-15 |
|  10009 | 1952-04-19 | Sumant     | Peac      | F      | 1985-02-18 |
|  10010 | 1963-06-01 | Duangkaew  | Piveteau  | F      | 1989-08-24 |
+--------+------------+------------+-----------+--------+------------+
10 rows in set (0.00 sec)
#统计各部门曾经拥有的员工数量
mysql> select dept_no,count(*) emp_sum
    -> from dept_emp
    -> group by dept_no
    -> order by emp_sum desc;
+---------+---------+
| dept_no | emp_sum |
+---------+---------+
| d005    |   85707 |
| d004    |   73485 |
| d007    |   52245 |
| d009    |   23580 |
| d008    |   21126 |
| d001    |   20211 |
| d006    |   20117 |
| d003    |   17786 |
| d002    |   17346 |
+---------+---------+
9 rows in set (0.63 sec)
#创建视图
mysql> CREATE VIEW test AS
    -> SELECT dept_no, COUNT(*) AS emp_sum
    -> FROM dept_emp
    -> GROUP BY dept_no
    -> ORDER BY emp_sum DESC
    -> ;
Query OK, 0 rows affected (0.16 sec)
mysql> select * from test;
+---------+---------+
| dept_no | emp_sum |
+---------+---------+
| d005    |   85707 |
| d004    |   73485 |
| d007    |   52245 |
| d009    |   23580 |
| d008    |   21126 |
| d001    |   20211 |
| d006    |   20117 |
| d003    |   17786 |
| d002    |   17346 |
+---------+---------+
9 rows in set (0.11 sec)
#联合查询，加上部门名称
mysql> select test.dept_no,emp_sum,dept_name
    -> from test,departments
    -> where test.dept_no = departments.dept_no;
+---------+---------+--------------------+
| dept_no | emp_sum | dept_name          |
+---------+---------+--------------------+
| d009    |   23580 | Customer Service   |
| d005    |   85707 | Development        |
| d002    |   17346 | Finance            |
| d003    |   17786 | Human Resources    |
| d001    |   20211 | Marketing          |
| d004    |   73485 | Production         |
| d006    |   20117 | Quality Management |
| d008    |   21126 | Research           |
| d007    |   52245 | Sales              |
+---------+---------+--------------------+
9 rows in set (0.16 sec)

cat filename | tail -n +3000 | head -n 1000

cat filename| head -n 3000 | tail -n +1000

cat -n textfile1 > textfile2

cat -b textfile1 textfile2 >> textfile3

cat /dev/null > /etc/test.txt

npm install hexo-generator-searchdb --save

npm install hexo-generator-searchdb --save