MySQL day1---初涉MySQL 基本操作 数据类型 约束
2017-09-16 20:10
756 查看
因为web课的课设，今天竟然神不知鬼不觉的看了一部分MySQL的javaweb网课，感觉还是有收获。既然毫不知觉的开始看了，希望自己能坚持下来。附上网课地址，感觉很全面，希望能看完（希望不是flag）。http://www.imooc.com/course/programdetail/pid/31
--Chapter 1--------------------------------------------------------------------------------------------------------------
MySQL登录：mysql -u账户 -p密码 (这应该是最简单的登录方式了 还有可以 eg:mysql -uroot -p -P3306 -h127.0.0.1）
MySQL退出：exit; 或者 quit; 或者 \q;
修改MySQL命令提示符：PROMPT
eg:
mysql>prompt \u@\h \d>
PROMPT set to '\u@\h \d>'
root@localhost (none)>
查看MySQL版本:SELECT VERSION()
eg:
root@localhost (none)>SELECT VERSION();
+------------+
| VERSION() |
+------------+
| 5.7.19-log |
+------------+
1 row in set (0.00 sec)
查看用户：SELECT USER();
eg:
root@localhost (none)>SELECT USER();
+----------------+
| USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
创建数据库:CREATE DATABASE table_name;
eg:
mysql>CREATE DATABASE t1;
Query OK, 1 row affected (0.00 sec)
展示所有数据库:SHOW DATABASE;
eg:
mysql>SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| t1 |
+--------------------+
5 rows in set (0.00 sec)
查看指定数据库：SHOW CREATE DATABASE table_name;
eg:
mysql>SHOW CREATE DATABASE t1;
+----------+-------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------+
| t1 | CREATE DATABASE `t1` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-------------------------------------------------------------+
1 row in set (0.00 sec)
特定方式创建数据库：CREATE DATABASE IF NOT EXISTS table_name CHARACTER SET gbk;
eg:
mysql>CREATE DATABASE IF NOT EXISTS t2 CHARACTER SET gbk;
Query OK, 1 row affected (0.00 sec)
mysql>SHOW CREATE DATABASE t2;
+----------+------------------------------------------------------------+
| Database | Create Database |
+----------+------------------------------------------------------------+
| t2 | CREATE DATABASE `t2` /*!40100 DEFAULT CHARACTER SET gbk */ |
+----------+------------------------------------------------------------+
1 row in set (0.00 sec)
修改指定数据库的编码方式：ALTER DATABASE t2 CHARACTER SET utf8;
eg:
mysql>ALTER DATABASE t2 CHARACTER SET utf8;
Query OK, 1 row affected (0.00 sec)
mysql>SHOW CREATE DATABASE t2;
+----------+-------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------+
| t2 | CREATE DATABASE `t2` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-------------------------------------------------------------+
1 row in set (0.00 sec)
删除指定数据库：DROP DATABASE table_name;
eg:
mysql>DROP DATABASE t1;
Query OK, 0 rows affected (0.01 sec)
mysql>SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| t2 |
+--------------------+
5 rows in set (0.00 sec)
如果存在的情况下删除（防止出错）：DROP DATABASE if exists table_name;
eg:
mysql>DROP DATABASE T1;
ERROR 1008 (HY000): Can't drop database 't1'; database doesn't exist
mysql>DROP DATABASE if exists T1;
Query OK, 0 rows affected, 1 warning (0.00 sec)
展示警告：SHOW WARNINGS;
[b]--Chapter 2--------------------------------------------------------------------------------------------------------------<
4000
/span>
[/b]
数据类型：
1.整型：
类别 字节数
TINYINT 1
SMALLINT 2
MEDIUMINT 3
INT 4
BIGINT 8
2.浮点型
FLOAT 单精度 E 38
DOUBLE 双精度 E 308
3.日期时间型
YEAR 1
TIME 3
DATE 3
DATETIME 8
TIMESTAMP 4
4.字符型
CHAR(M) M个字节
VERCHAR(M)
TINYTEST L+1
TEXT L+2
MEDIUMTEXT L+3
LONGTEXT L+4
ENUM 1/2 字节
SET 1 2 3 4 / 8字节（排列组合）
数据表：
行记录 列字段
插入记录 查找记录
创建数据表 约束使用
创建数据表：
CREATE TABLE tb1(
-> username VARCHAR(20),
->age TINYINT(3) UNSIGNED,
->salary FLOAT(8,2)
-> );
查看数据表：SHOW COLUMNS FROM tb1;
插入记录：INSERT tb1 VALUES('TOM',25,7584.23);
插入特定项:INSERT tb1(username,salary) VALUES('JOHN',8000);
查看所有记录：SELECT * FROM tb1;
插入非空项：CREATE TABLE tb2(
-> username VARCHAR(20) NOT NULL,
-> age TINYINT UNSIGNED NULL,
-> salare float(8.2) NULL
-> );
eg:
mysql> CREATE TABLE tb2(
-> username VARCHAR(20) NOT NULL,
-> age TINYINT UNSIGNED NULL,
-> salare float(8.2) NULL
-> );
Query OK, 0 rows affected (0.21 sec)
mysql> SHOW COLUMNS FROM tb2;
+----------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------------+------+-----+---------+-------+
| username | varchar(20) | NO | | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
| salare | float | YES | | NULL | |
+----------+---------------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
此时插入的数据项 username不能为NULL
mysql> INSERT tb2 VALUES(NULL,25,13141);
ERROR 1048 (23000): Column 'username' cannot be null
主值约束：
eg:
mysql> CREATE TABLE tb3(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL
-> );
Query OK, 0 rows affected (0.23 sec)
mysql> SHOW COLUMNS FROM tb3;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
AUTO_INCREMENT 一定主值 主值不一定AUTO_INCREMENT
mysql> INSERT tb3(username) VALUES('John');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT tb3(username) VALUES('Rose');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT tb3(username) VALUES('Dim');
Query OK, 1 row affected (0.06 sec)
mysql> SELECT * FROM tb3
-> ;
+----+----------+
| id | username |
+----+----------+
| 1 | TOM |
| 2 | John |
| 3 | Rose |
| 4 | Dim |
+----+----------+
4 rows in set (0.00 sec)
mysql> CREATE TABLE tb4(
-> id SMALLINT UNSIGNED PRIMARY KEY,
-> username VARCHAR(20) NOT NULL
-> );
Query OK, 0 rows affected (0.30 sec)
mysql> SHOW COLUMNS FROM tb4;
+----------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+-------+
| id | smallint(5) unsigned | NO | PRI | NULL | |
| username | varchar(20) | NO | | NULL | |
+----------+----------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> INSERT tb4 VALUES(4,'TOM');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT tb4 VALUES(22,'TOM');
Query OK, 1 row affected (0.08 sec)
mysql>
mysql> SELECT * FROM tb4;
+----+----------+
| id | username |
+----+----------+
| 4 | TOM |
| 22 | TOM |
+----+----------+
2 rows in set (0.00 sec)
mysql> INSERT tb4 VALUES(22,'TOM');
ERROR 1062 (23000): Duplicate entry '22' for key 'PRIMARY'
主值保证不重复
仅可有一个
唯一约束：
eg:
mysql> CREATE TABLE tb5
-> (id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE KEY,
-> age tinyint UNSIGNED);
Query OK, 0 rows affected (0.45 sec)
mysql> SHOW COLUMNS FROM tb5;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | UNI | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> INSERT tb5(username,age) VALUE('T0M',22);
Query OK, 1 row affected (0.08 sec)
mysql> INSERT tb5(username,age) VALUE('T0M',22);
ERROR 1062 (23000): Duplicate entry 'T0M' for key 'username'
唯一约束可有多个
默认约束：
eg:
mysql> CREATE TABLE tb7(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE KEY,
-> sex ENUM('1','2','3') DEFAULT 3);
Query OK, 0 rows affected (0.25 sec)
mysql> SHOW COLUMNS FROM tb7
-> ;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | UNI | NULL | |
| sex | enum('1','2','3') | YES | | 3 | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> INSERT tb7(username) values('TOM');
Query OK, 1 row affected (0.06 sec)
mysql> SELECT * FROM tb7;
+----+----------+------+
| id | username | sex |
+----+----------+------+
| 1 | TOM | 3 |
+----+----------+------+
1 row in set (0.00 sec)
前两章就这些了，图书馆要闭馆了，最后写的有些凌乱 。继续加油！
--Chapter 1--------------------------------------------------------------------------------------------------------------
MySQL登录：mysql -u账户 -p密码 (这应该是最简单的登录方式了 还有可以 eg:mysql -uroot -p -P3306 -h127.0.0.1）
MySQL退出：exit; 或者 quit; 或者 \q;
修改MySQL命令提示符：PROMPT
eg:
mysql>prompt \u@\h \d>
PROMPT set to '\u@\h \d>'
root@localhost (none)>
查看MySQL版本:SELECT VERSION()
eg:
root@localhost (none)>SELECT VERSION();
+------------+
| VERSION() |
+------------+
| 5.7.19-log |
+------------+
1 row in set (0.00 sec)
查看用户：SELECT USER();
eg:
root@localhost (none)>SELECT USER();
+----------------+
| USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
创建数据库:CREATE DATABASE table_name;
eg:
mysql>CREATE DATABASE t1;
Query OK, 1 row affected (0.00 sec)
展示所有数据库:SHOW DATABASE;
eg:
mysql>SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| t1 |
+--------------------+
5 rows in set (0.00 sec)
查看指定数据库：SHOW CREATE DATABASE table_name;
eg:
mysql>SHOW CREATE DATABASE t1;
+----------+-------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------+
| t1 | CREATE DATABASE `t1` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-------------------------------------------------------------+
1 row in set (0.00 sec)
特定方式创建数据库：CREATE DATABASE IF NOT EXISTS table_name CHARACTER SET gbk;
eg:
mysql>CREATE DATABASE IF NOT EXISTS t2 CHARACTER SET gbk;
Query OK, 1 row affected (0.00 sec)
mysql>SHOW CREATE DATABASE t2;
+----------+------------------------------------------------------------+
| Database | Create Database |
+----------+------------------------------------------------------------+
| t2 | CREATE DATABASE `t2` /*!40100 DEFAULT CHARACTER SET gbk */ |
+----------+------------------------------------------------------------+
1 row in set (0.00 sec)
修改指定数据库的编码方式：ALTER DATABASE t2 CHARACTER SET utf8;
eg:
mysql>ALTER DATABASE t2 CHARACTER SET utf8;
Query OK, 1 row affected (0.00 sec)
mysql>SHOW CREATE DATABASE t2;
+----------+-------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------+
| t2 | CREATE DATABASE `t2` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-------------------------------------------------------------+
1 row in set (0.00 sec)
删除指定数据库：DROP DATABASE table_name;
eg:
mysql>DROP DATABASE t1;
Query OK, 0 rows affected (0.01 sec)
mysql>SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| t2 |
+--------------------+
5 rows in set (0.00 sec)
如果存在的情况下删除（防止出错）：DROP DATABASE if exists table_name;
eg:
mysql>DROP DATABASE T1;
ERROR 1008 (HY000): Can't drop database 't1'; database doesn't exist
mysql>DROP DATABASE if exists T1;
Query OK, 0 rows affected, 1 warning (0.00 sec)
展示警告：SHOW WARNINGS;
[b]--Chapter 2--------------------------------------------------------------------------------------------------------------<
4000
/span>
[/b]
数据类型：
1.整型：
类别 字节数
TINYINT 1
SMALLINT 2
MEDIUMINT 3
INT 4
BIGINT 8
2.浮点型
FLOAT 单精度 E 38
DOUBLE 双精度 E 308
3.日期时间型
YEAR 1
TIME 3
DATE 3
DATETIME 8
TIMESTAMP 4
4.字符型
CHAR(M) M个字节
VERCHAR(M)
TINYTEST L+1
TEXT L+2
MEDIUMTEXT L+3
LONGTEXT L+4
ENUM 1/2 字节
SET 1 2 3 4 / 8字节（排列组合）
数据表：
行记录 列字段
插入记录 查找记录
创建数据表 约束使用
创建数据表：
CREATE TABLE tb1(
-> username VARCHAR(20),
->age TINYINT(3) UNSIGNED,
->salary FLOAT(8,2)
-> );
查看数据表：SHOW COLUMNS FROM tb1;
插入记录：INSERT tb1 VALUES('TOM',25,7584.23);
插入特定项:INSERT tb1(username,salary) VALUES('JOHN',8000);
查看所有记录：SELECT * FROM tb1;
插入非空项：CREATE TABLE tb2(
-> username VARCHAR(20) NOT NULL,
-> age TINYINT UNSIGNED NULL,
-> salare float(8.2) NULL
-> );
eg:
mysql> CREATE TABLE tb2(
-> username VARCHAR(20) NOT NULL,
-> age TINYINT UNSIGNED NULL,
-> salare float(8.2) NULL
-> );
Query OK, 0 rows affected (0.21 sec)
mysql> SHOW COLUMNS FROM tb2;
+----------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------------+------+-----+---------+-------+
| username | varchar(20) | NO | | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
| salare | float | YES | | NULL | |
+----------+---------------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
此时插入的数据项 username不能为NULL
mysql> INSERT tb2 VALUES(NULL,25,13141);
ERROR 1048 (23000): Column 'username' cannot be null
主值约束：
eg:
mysql> CREATE TABLE tb3(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL
-> );
Query OK, 0 rows affected (0.23 sec)
mysql> SHOW COLUMNS FROM tb3;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
AUTO_INCREMENT 一定主值 主值不一定AUTO_INCREMENT
mysql> INSERT tb3(username) VALUES('John');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT tb3(username) VALUES('Rose');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT tb3(username) VALUES('Dim');
Query OK, 1 row affected (0.06 sec)
mysql> SELECT * FROM tb3
-> ;
+----+----------+
| id | username |
+----+----------+
| 1 | TOM |
| 2 | John |
| 3 | Rose |
| 4 | Dim |
+----+----------+
4 rows in set (0.00 sec)
mysql> CREATE TABLE tb4(
-> id SMALLINT UNSIGNED PRIMARY KEY,
-> username VARCHAR(20) NOT NULL
-> );
Query OK, 0 rows affected (0.30 sec)
mysql> SHOW COLUMNS FROM tb4;
+----------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+-------+
| id | smallint(5) unsigned | NO | PRI | NULL | |
| username | varchar(20) | NO | | NULL | |
+----------+----------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> INSERT tb4 VALUES(4,'TOM');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT tb4 VALUES(22,'TOM');
Query OK, 1 row affected (0.08 sec)
mysql>
mysql> SELECT * FROM tb4;
+----+----------+
| id | username |
+----+----------+
| 4 | TOM |
| 22 | TOM |
+----+----------+
2 rows in set (0.00 sec)
mysql> INSERT tb4 VALUES(22,'TOM');
ERROR 1062 (23000): Duplicate entry '22' for key 'PRIMARY'
主值保证不重复
仅可有一个
唯一约束：
eg:
mysql> CREATE TABLE tb5
-> (id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE KEY,
-> age tinyint UNSIGNED);
Query OK, 0 rows affected (0.45 sec)
mysql> SHOW COLUMNS FROM tb5;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | UNI | NULL | |
| age | tinyint(3) unsigned | YES | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> INSERT tb5(username,age) VALUE('T0M',22);
Query OK, 1 row affected (0.08 sec)
mysql> INSERT tb5(username,age) VALUE('T0M',22);
ERROR 1062 (23000): Duplicate entry 'T0M' for key 'username'
唯一约束可有多个
默认约束：
eg:
mysql> CREATE TABLE tb7(
-> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
-> username VARCHAR(20) NOT NULL UNIQUE KEY,
-> sex ENUM('1','2','3') DEFAULT 3);
Query OK, 0 rows affected (0.25 sec)
mysql> SHOW COLUMNS FROM tb7
-> ;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| username | varchar(20) | NO | UNI | NULL | |
| sex | enum('1','2','3') | YES | | 3 | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> INSERT tb7(username) values('TOM');
Query OK, 1 row affected (0.06 sec)
mysql> SELECT * FROM tb7;
+----+----------+------+
| id | username | sex |
+----+----------+------+
| 1 | TOM | 3 |
+----+----------+------+
1 row in set (0.00 sec)
前两章就这些了，图书馆要闭馆了，最后写的有些凌乱 。继续加油！
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