MySQL數據庫管理

SQL語句概述

SQL語言

• 是Structured Query Language的縮寫，即結構化查詢語言
• 是關系型數據庫的標準語言
• 用于維護管理數據庫，如數據查詢、數據更新、訪問控制、對象管理等功能

SQL分類

（1）DDL：數據定義語言
（2）DML：數據操縱語言
（3）DQL：數據查詢語言
（4）DCL：數據控制語言

DDL操作命令

1、DDL語句用于創建數據庫對象，如庫、表、索引等

2、使用DDL語句新建庫、表

（1）創建數據庫：creste databaes 數據庫名
（2）創建數據表：create table 表名 （字段定義……)

3、使用DDL語句刪除庫、表

（1）刪除指定的數據表：drop table [數據庫名]表名
（2）刪除指定的數據庫：drop database 數據庫名

DML操作命令

1、DML語句用于對表中的數據進行管理

2、包括以下操作

（1）insert：插入新數據
（2）update：更新原有數據
（3）delete：刪除不需要的數據

3、向數據表中插入新的數據記錄

insert into 表名(字段1,字段2, .....) values(字段1的值,字段的值, .....)

4、修改、更新數據表P F的數據記錄

update 表名 set 字段名1=值1[,字段名2=值2] where 條件表達式

5、在數據表中刪除指定的數據記錄

（1）delete from 表名 where 條件表達式
（2）不帶where條件的語句表示刪除表中所有記錄(謹慎操作)

DQL操作命令

1、DQL是數據查詢語句，只有一條: SELECT

2、用于從數據表中查找符合條件的數據記錄

3、查詢時可不指定條件

selext 字段名1,字段名2..... from 表名;

4、查詢時指定條件

select 字段名1,字段名2.... from 表名 where 條件表達式;

DCL語句操作

1、設置用戶權限(用戶不存在時，則新建用戶)

GRANT 權限列表 ON 數據庫名.表名 TO 用戶名@來源地址 [ IDENTIFIED BY‘密碼’ ]

2、查看用戶的權限

SHOW GRANTS FOR 用戶名@來源地址

3、撤銷用戶的權限

REVOKE 權限列表 ON 數據庫名.表名 FROM 用戶名@來源地址

操作實例

1、查看數據庫列表信息

mysql> show databases;    //查看數據庫列表信息
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |                     //其中mysql為系統數據庫
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.02 sec)

2、創建數據庫

mysql> create database school;    //創建數據庫school
Query OK, 1 row affected (0.02 sec)

mysql> show databases;      //查看數據庫列表信息
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |                //成功創建數據庫
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> 

3、創建表

mysql> 
mysql> use school;   //使用數據庫school
Database changed
mysql> show tables;
Empty set (0.00 sec)

mysql> create table info (
    -> id int(4) not null,
    -> name char(10) not null,
    -> address varchar(50) default 'beijing',
    -> score decimal,
    -> primary key(id));   //創建表info
Query OK, 0 rows affected (0.01 sec)

mysql> describe info;   //查看表結構
+---------+---------------+------+-----+---------+-------+
| Field   | Type          | Null | Key | Default | Extra |
+---------+---------------+------+-----+---------+-------+
| id      | int(4)        | NO   | PRI | NULL    |       |
| name    | char(10)      | NO   |     | NULL    |       |
| address | varchar(50)   | YES  |     | beijing |       |
| score   | decimal(10,0) | YES  |     | NULL    |       |
+---------+---------------+------+-----+---------+-------+
4 rows in set (0.03 sec)

4、表中添加數據與查看表中數據

mysql> 
mysql> insert into info (id,name,address,score) values (1,'stu01','shanghai',88);   //添加數據
Query OK, 1 row affected (0.03 sec)

mysql> insert into info (id,name,address,score) values (2,'stu02','nanjing',79);   //添加數據
Query OK, 1 row affected (0.01 sec)

mysql> insert into info (id,name,address,score) values (3,'stu03',default,90);   //添加數據
Query OK, 1 row affected (0.00 sec)

mysql> insert into info (id,name,address,score) values (4,'stu04','',60);   //添加數據
Query OK, 1 row affected (0.00 sec)

mysql> select * from info;    //查看info表中數據
+----+-------+----------+-------+
| id | name  | address  | score |
+----+-------+----------+-------+
|  1 | stu01 | shanghai |    88 |
|  2 | stu02 | nanjing  |    79 |
|  3 | stu03 | beijing  |    90 |
|  4 | stu04 |          |    60 |
+----+-------+----------+-------+
4 rows in set (0.00 sec)

5、修改與刪除表中數據

mysql> update info set address='hangzhou' where id=4 and name='stu04';   //修改id為4的address為“hangzhou”
Query OK, 1 row affected (0.04 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from info;   //查看表中數據
+----+-------+----------+-------+
| id | name  | address  | score |
+----+-------+----------+-------+
|  1 | stu01 | shanghai |    88 |
|  2 | stu02 | nanjing  |    79 |
|  3 | stu03 | beijing  |    90 |
|  4 | stu04 | hangzhou |    60 |
+----+-------+----------+-------+
4 rows in set (0.01 sec)

mysql> delete from info where name='stu04';   //刪除表中name為“stu04”的數據
Query OK, 1 row affected (0.02 sec)

mysql> select * from info;   //查看表中數據
+----+-------+----------+-------+
| id | name  | address  | score |
+----+-------+----------+-------+
|  1 | stu01 | shanghai |    88 |
|  2 | stu02 | nanjing  |    79 |
|  3 | stu03 | beijing  |    90 |
+----+-------+----------+-------+
3 rows in set (0.00 sec)

6、刪除表和數據庫

mysql> drop table info;   //刪除表info
Query OK, 0 rows affected (0.06 sec)

mysql> show tables;   //查看表，刪除成功
Empty set (0.00 sec)

mysql> drop database school;   //刪除數據庫
Query OK, 0 rows affected (0.04 sec)

mysql> show databases;   //查看數據庫，刪除成功
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

7、設置、查看與撤銷用戶權限

mysql> show grants for 'root'@'%';   //查看權限
+-------------------------------------------------------------+
| Grants for root@%                                           |
+-------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION |
+-------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> revoke all on *.* from 'root'@'%';   //刪除權限
Query OK, 0 rows affected (0.03 sec)

mysql> show grants for 'root'@'%';   //查看權限
+----------------------------------------------------+
| Grants for root@%                                  |
+----------------------------------------------------+
| GRANT USAGE ON *.* TO 'root'@'%' WITH GRANT OPTION |
+----------------------------------------------------+
1 row in set (0.00 sec)

mysql> grant all on *.* to root@'%' identified by 'abc123';   //添加權限
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show grants for 'root'@'%';   //查看權限
+-------------------------------------------------------------+
| Grants for root@%                                           |
+-------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION |
+-------------------------------------------------------------+
1 row in set (0.00 sec)

mysql>