7 May 18
1. Database related concepts
1. Two hardware expansion methods
a. Vertical expansion: for one computer
b. Horizontal expansion: multiple ordinary computers
2. Database related concepts
Database server (essentially a computer on which the server of database management software is installed) -- referred to as database (operation and maintenance perspective)
Database management system RDBMS (essentially a socket software with a C/S architecture) -- referred to as database (operation and maintenance perspective)
Note: The server side of the general database management system is installed on the linux operating system
mysqld——server; mysql——client (python can't use the server that comes with mysql, you need to use pymysql)
a. Support concurrency
b, lock problem
c. Authenticate client requests
d. Access efficiency (reduce the number of IOs)
Library (folder) -- referred to as database (programmer's perspective)
Table (file): fields to be set (header)
Record: extract all typical features/data of a thing (a collection of a bunch of data)
egon, 18,180, male, True
data:
name='egon' age=18 height=180 sex="male" beutiful=True
SQL statement: The SQL statements used/defined by different database software are not exactly the same, but the difference is not big
3. Database management system/software classification DBMS:
Relational RDBMS:
There is a table structure, the table structure must be defined before accessing data, and the data must be stored according to the type or constraint of the field
Typical representatives: MySQL, Oracle, DB2, SQL server (commonly used in the banking industry)
Non-relational (commonly used by reptiles):
Accessing data is in the form of key:value
Non-relational: Mongodb, redis, memcache (less commonly used)
2. Basic management (windows system)
1. Installation (installation is completed after the Windows system decompresses the file)
2. Add environment variables
3. Make mysqld software a system service
Note: Turn off mysqld before making
C:\Windows\system32>tasklist |findstr mysqld
mysqld.exe 8372 Console 2 454,916 K
C:\Windows\system32>taskkill /F /PID 8372
Success: Process with PID 8372 terminated.
Make:
mysqld --install
Check:
windows + r
Enter services.msc
4. Start:
Unmade system service startup method:
1. Start the server
mysqld
2. Start the client
mysql -uroot -p -h127.0.0.1 -P 3306 #3306 is the default port for mysql
If you log in to the mysqld server locally, you can abbreviate it: mysql -uroot -p #The local IP is known, and the port defaults
After creating the system service, you can click the mouse to start or close mysql:
windows + r
Enter services.msc
find mysql, start or close
5. Crack the administrator password
1. First close the mysqld server
2. Start the mysqld server on the command line by skipping the authorization table
mysqld --skip-grant-tables
3. The client directly logs in to the root user without a password and changes the password
mysql -uroot -p
mysql> update mysql.user set password=password("123") where user="root" and host="localhost";
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
mysql> flush privileges; #Force refresh after each change
Query OK, 0 rows affected (0.00 sec)
4. Kill the mysqld service with taskkill on the command line, and then start mysqld normally
taskkill /F /PID 131312
def password(mingwen): #password module can help encrypt plaintext, just call it directly
import hashlib
m=hashlib.md5()
m.update(mimgwen)
return m.hexdigest()
6. Unified character encoding
1. Create a new my.ini file in the mysql installation directory
2. Modify my.ini
[mysqld]
character-set-server=utf8
collation-server=utf8_general_ci
[client]
default-character-set=utf8
[mysql]
default-character-set=utf8
3. Restart mysqld
4. Client login, enter \s to view the results
3. Basic management (mac system)
1. Installation (mysql-5.6.35-macos10.12-x86_64.dmg)
2. Add environment variables
https://blog.csdn.net/con_heart/article/details/53766931
In fact, like windows, adding environment variables to the advanced properties is to find the command when you enter a command in any path, so you don't have to enter the file where the command is located every time you want to enter a command (such as logging in to mysql). Clip (usually quite long). The following is to add the path of the mysql command to the environment variable:
1. Open the terminal and enter: cd ~
will enter the ~ folder
2. Then enter: touch .bash_profile
After the carriage return is executed,
3. Enter again: open -e .bash_profile
will open the file in TextEdit (if no environment variables have been configured before, this should be a blank document). If there is content, please enter it before the terminator, if there is no content, please enter the following statement directly: export PATH=${PATH}:/usr/local/mysql/bin
Then, save, quit TextEdit (must be quit), close the terminal and quit.
4. Open the terminal again, directly enter [mysql -u "your user name" -p ], press Enter and enter the password. At this time, you can log in to mysql
3. View the mysql folder
Go to the folder -> /usr/local/mysql
4. Start:
Finder -> System Preferences
PATH="$PATH":/usr/local/mysql/bin
mysql -u root -p #-p do not add a space, directly connect to the password
5. Crack the administrator password
https://blog.csdn.net/lishaojun0115/article/details/52805563
step1: Apple -> System Preferences -> Click MySQL at the bottom to close the mysql service in the pop-up page (click stop mysql server)
step2: Enter the terminal and enter: cd /usr/local/mysql/bin/
After pressing Enter, log in with administrator privileges sudo su
Enter the following command after pressing Enter to disable the mysql authentication function./mysqld_safe --skip-grant-tables &
After pressing Enter, mysql will automatically restart (the status of mysql in the preferences will change to running)
step3：
Enter the command ./mysql
After pressing Enter, enter the command FLUSH PRIVILEGES;
After pressing Enter, enter the command SET PASSWORD FOR 'root'@'localhost' = PASSWORD('your new password');
At this point, the password modification is completed, and you can log in successfully.
6. Unified character encoding (to prevent garbled characters, unified into utf-8)
1. Copy the my.cnf file and add the following to it
[mysqld]
character-set-server=utf8
collation-server=utf8_general_ci
#basedir=/usr/local/mysql/
#datadir=/usr/local/mysql/data/
[client]
default-character-set=utf8
user=root
password=******
[mysql]
default-character-set=utf8
#sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
2. Close the mysql server
3. Add my.cnf under \etc
4. Restart the mysql server, log in to the client and view (\s)
7. Others:
MAC computer to install Mysql server and Navicat for mysql client
https://blog.csdn.net/kuangdacaikuang/article/details/76515985
Fourth, the basic SQL statement
#The main operation objects of SQL statements are libraries, tables, and records; among which operations on records are the most common
1. Folder (library) # The library name can be named according to the python naming rules
increase
create database db1 charset utf8;
change
alter database db1 charset gbk; #The library name cannot be modified
check
View library names of all libraries
show databases; #where information_scheme is an in-memory table
View information about a library alone
show create database db1;
delete
drop database db1;
2. File (table) #Table name can be named according to python's naming rules
First switch folders:
use db1; #Can also be called by subsequent db1.t1
select database(); #View the current folder
increase
create table t1(id int,name char); #char is str in sql
change
alter table t1 modify name char(16); #16 is the access limit, up to 16 characters can be accessed
check
View all table names under the current library
show tables;
View details of t1 table
show create table t1;
View table structure
desc t1;
delete
drop table t1;
3. One line of the file (record)
increase
insert into db1.t1 values
(1,'egon'), #Before adding, it is best to check the charset of the previous table
(2,'alex'),
(3,'lxx');
change
update db1.t1 set name='sb' where id > 1;
check
select id,name from db1.t1;
delete
delete from db1.t1 where name = "SB" ;
4, ; is the statement end prompt for the SQL statement
\c If the statement is wrong, use it when you want to exit each input without affecting the result
5. Storage engine
#Thread pool used by Mysql
create table t1(id int)engine=innodb;
create table t2(id int)engine=myisam;
create table t3(id int)engine=blackhole;
create table t4(id int)engine=memory;
Common innodb, myisam, memory, blackhole several storage engines, the most commonly used is innodb innodb: also the default storage engine, supports transactions, row lock design, foreign keys
t1.frm (frame) t1.ibd (innodb data); save to hard disk
myisam: t2.MYD (myisam data) t2.MYI (myisam index) t2.frm (frame); save to hard disk
blackhole: t3.frm
memory: t4.frm; Stored in memory, after closing the server, the data is cleared