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MySQL (1) -- related concepts, SQL classification, and simple operations
2022-07-05 23:13:00 【Dutkig】
One 、 database ？ Database management system ？SQL？ What is the relationship ？
database ： English words DataBase, abbreviation DB. A combination of files that store data in a certain format .
seeing the name of a thing one thinks of its function ： A warehouse for storing data , It's actually a bunch of files . These files store Data with a specific format .Database management system ： DataBaseManagement, abbreviation DBMS.
Database management system is specially used to manage the data in the database , Database management system can Add, delete, modify and query the data in the database .Common database management system ： MySQL、Oracle、MS SqlServer、DB2、sybase etc. …
SQL： Structured query language Programmers need to learn SQL sentence , Programmers write SQL sentence , then DBMS Responsible for the execution of SQL sentence , Finally to complete the database of data addition, deletion, modification and query operation .
SQL It's a set of standards , What programmers mainly learn is SQL sentence , This SQL stay mysql Can be used in , At the same time Oracle Can also be used in , stay DB2 Can also be used in .
The relationship between the three
DBMS– perform –> SQL -- operation –> DB
SQL The classification of sentences
SQL There are many sentences , It's best to classify , It's easier to remember , It is divided into ：
DQL： Data query language （ Usually with select Keywords are all query statements ）select…
DML： Data operation language （ All additions, deletions and modifications to the data in the table are DML）insert delete update（ This is mainly the data in the operation table data）.
DDL： Data definition language （ Usually with create、drop Delete 、alter All the changes are DDL）. The main operation is the table structure . Not the data in the table .
—— This addition, deletion, modification and DML Different , This is mainly used to operate the table structure .TCL： Transaction control language , Include ： Transaction submission ：commit and Transaction rollback ：rollback;
DCL： Data control language . for example ： to grant authorization grant、 Revoke authority revoke…
Two 、 Look at the services on the computer , Look for it MySQL Where is your service ？
Computer --> Right click --> management --> Services and Applications --> service --> look for mysql service
MySQL Service for , The default is “ start-up ” The state of , It's only activated mysql Ability to use .
By default “ Automatically ” start-up , Auto start means the next time you restart the operating system
Automatically start the service .
You can right-click on the service ：
start-up
Restart the service
Out of Service
...
You can also change the default configuration of the service ：
Right click on the service , attribute , Then you can choose the startup mode ：
Automatically （ Delayed start ）
Automatically
Manual
Ban
3、 ... and 、windows Startup and shutdown in the operating system mysql Service? ？
grammar ：
net stop The service name ;
net start The service name ;
The above commands can be used to start and stop other services .
Four 、mysql Installed , Service started , How to use client login mysql Database ？
Use bin In the catalog mysql.exe Command to connect mysql database server
Log in locally （ Show the form of writing a password ）：
C:\Users\Administrator>mysql -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.36 MySQL Community Server (GPL)
Copyright (c) 2000, 2014, 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>
Log in locally （ In the form of hidden passwords ）：
C:\Users\Administrator>mysql -uroot -p
Enter password: ******
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.5.36 MySQL Community Server (GPL)
Copyright (c) 2000, 2014, 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>
5、 ... and 、mysql Common commands
sign out mysql ：
exitsee mysql Which databases are in ？
Be careful： It ends with a semicolon .
show databases;
mysql By default, it comes with 4 A database .
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
- Choose to use a database
use databases;
mysql> use sys;
Database changed
Indicates that you are using a name called sys The database of .
- Create database
create database name;
mysql> create database mk;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mk |
| mysql |
| performance_schema |
| sys |
+--------------------+
- Check which tables are under a database ？
show tables;
mysql> show tables;
Be careful ： The above commands are not case sensitive , Will do .
- see mysql Version number of the database ：
mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.11 |
+-----------+
1 row in set (0.00 sec)
- Check which database you are currently using ？
mysql> select database();
+-------------+
| database() |
+-------------+
| mk |
+-------------+
6、 ... and 、 The most basic unit in the database is the table ：table
What is a watch table？ Why use tables to store data ？
full name Gender Age ( Column ： Field )
---------------------------
Zhang San male 20 -------> That's ok （ Record ）
Li Si Woman 21 -------> That's ok （ Record ）
Wang Wu male 22 -------> That's ok （ Record ）
The data in the database is represented in the form of tables . Because the table is more intuitive .
Any table has rows and columns ：
That's ok （row）： It's called data / Record .
Column （column）： It's called a field . such as ： Name field 、 Gender field 、 Age field .
Get to know ：
Every field has ： Field name 、 data type 、 Constraints, etc .
The field name is understandable , It's an ordinary name , Just see the name and know the meaning .
data type ： character string , Numbers , Date, etc.
constraint ： There are also many constraints , One of them is called uniqueness constraint ,
7、 ... and 、 Complete some simple operations
Prepare one in advance test.sql Database table of . How to integrate sql What about the data import in the file ？
mysql> source C:\Desktop\test.sql ` Be careful `： No Chinese in the path ！！！！
Query OK, 0 rows affected, 1 warning (0.01 sec)
Query OK, 0 rows affected, 1 warning (0.00 sec)
Query OK, 0 rows affected, 1 warning (0.00 sec）
Query OK, 0 rows affected (0.10 sec）
Query OK, 0 rows affected (0.01 sec）
Query OK, 0 rows affected (0.01 sec）
Query OK, 1 row affected (0.01 sec）
Query OK, 1 row affected (0.00 sec）
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec）
Query OK, 0 rows affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 1 row affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> show tables;
+-----------------------+
| Tables_in_test |
+-----------------------+
| dept |
| emp |
| salgrade |
+-----------------------+
notes ：
- dept It's a department table
- emp It's the staff watch
- salgrade It's the salary scale
View data in table
select * from Table name ;
mysql> select * from emp; // from emp Table queries all data .
+-------+--------+-----------+------+------------+---------+---------+--------+
| EMPNO | ENAME | JOB | MGR | HIREDATE | SAL | COMM | DEPTNO |
+-------+--------+-----------+------+------------+---------+---------+--------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | 0.00 | 30 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
+-------+--------+-----------+------+------------+---------+---------+--------+
mysql> select * from dept;
+--------+------------+----------+
| DEPTNO | DNAME | LOC |
+--------+------------+----------+
| 10 | ACCOUNTING | NEW YORK |
| 20 | RESEARCH | DALLAS |
| 30 | SALES | CHICAGO |
| 40 | OPERATIONS | BOSTON |
+--------+------------+----------+
mysql> select * from salgrade;
+-------+-------+-------+
| GRADE | LOSAL | HISAL |
+-------+-------+-------+
| 1 | 700 | 1200 |
| 2 | 1201 | 1400 |
| 3 | 1401 | 2000 |
| 4 | 2001 | 3000 |
| 5 | 3001 | 9999 |
+-------+-------+-------+
Don't look at the data in the table , Just look at the structure of the table
desc Table name ;//describe
mysql> desc dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| DEPTNO | int(2) | NO | PRI | NULL | | Department number
| DNAME | varchar(14) | YES | | NULL | | Department name
| LOC | varchar(13) | YES | | NULL | | Location
+--------+-------------+------+-----+---------+-------+
mysql> desc emp;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| EMPNO | int(4) | NO | PRI | NULL | | Employee number
| ENAME | varchar(10) | YES | | NULL | | Employee name
| JOB | varchar(9) | YES | | NULL | | jobs
| MGR | int(4) | YES | | NULL | | Superior number
| HIREDATE | date | YES | | NULL | | Date of entry
| SAL | double(7,2) | YES | | NULL | | Wages
| COMM | double(7,2) | YES | | NULL | | subsidy
| DEPTNO | int(2) | YES | | NULL | | Department number
+----------+-------------+------+-----+---------+-------+
mysql> desc salgrade;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| GRADE | int(11) | YES | | NULL | | Pay scale
| LOSAL | int(11) | YES | | NULL | | minimum wage
| HISAL | int(11) | YES | | NULL | | Maximum wage
+-------+---------+------+-----+---------+-------+
mysql> describe dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| DEPTNO | int(2) | NO | PRI | NULL | |
| DNAME | varchar(14) | YES | | NULL | |
| LOC | varchar(13) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
Next blog , We will enter SQL Sentence learning .
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