MySQL SQL介绍

Posted 2020-12-09 woaiyunwei

mysql SQL介绍(1)

目录

• MySQL SQL介绍(1)
  • 一、MySQL SQL介绍
    • 1.1.1 SQL 应用基础

一、MySQL SQL介绍

1.1.1 SQL 应用基础

1. 常用的列属性约束

1、primary  key      （主键） 
2、unique            （唯一）
3、not null          （不为空）
4、default           （默认值） 
5、auto_increment    （自增长）
6、unsigned             （无符号） 常与zerofill（零填充）配合
7、comment              （注释）

2. 创库建表插入数据回顾

#创建school
mysql> create database school character set utf8mb4 collate utf8mb4_general_ci;
Query OK, 1 row affected (0.00 sec)
mysql> Show collation;
+--------------------------+----------+-----+---------+----------+---------+
| Collation                | Charset  | Id  | Default | Compiled | Sortlen |
+--------------------------+----------+-----+---------+----------+---------+
| big5_chinese_ci          | big5     |   1 | Yes     | Yes      |       1 |
| big5_bin                 | big5     |  84 |         | Yes      |       1 |
| dec8_swedish_ci          | dec8     |   3 | Yes     | Yes      |       1 |
| dec8_bin                 | dec8     |  69 |         | Yes      |       1 |
| cp850_general_ci         | cp850    |   4 | Yes     | Yes      |       1 |
| cp850_bin                | cp850    |  80 |         | Yes      |       1 |
| hp8_english_ci           | hp8      |   6 | Yes     | Yes      |       1 |
| hp8_bin                  | hp8      |  72 |         | Yes      |       1 |
| koi8r_general_ci         | koi8r    |   7 | Yes     | Yes      |       1 |

mysql> use school
Database changed

#创建测试环境表
#学生表
mysql> create table student(
    ->  sno int not null primary key auto_increment comment ‘学号‘,
    ->  sname varchar(255) not null comment ‘学生姓名‘,
    ->  sage tinyint(3) unsigned zerofill not null comment ‘学生年龄‘,
    ->  ssex char(1) not null comment ‘学生性别‘
    ->  )engine=innodb charset=utf8mb4;
Query OK, 0 rows affected (0.00 sec)

mysql> desc student;
+-------+------------------------------+------+-----+---------+----------------+
| Field | Type                         | Null | Key | Default | Extra          |
+-------+------------------------------+------+-----+---------+----------------+
| sno   | int(11)                      | NO   | PRI | NULL    | auto_increment |
| sname | varchar(255)                 | NO   |     | NULL    |                |
| sage  | tinyint(3) unsigned zerofill | NO   |     | NULL    |                |
| ssex  | char(1)                      | NO   |     | NULL    |                |
+-------+------------------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

#教师表
mysql> create table teacher(
    -> tno int not null primary key auto_increment comment ‘教师编号‘,
    -> tname varchar(255) not null comment ‘教师名字‘
    -> )engine=innodb charset=utf8mb4;
Query OK, 0 rows affected (0.04 sec)

mysql> desc teacher;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| tno   | int(11)      | NO   | PRI | NULL    | auto_increment |
| tname | varchar(255) | NO   |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)

#课程表
mysql> create table course(
    -> cno int not null unique primary key auto_increment comment ‘课程编号‘,
    -> cname varchar(255) unique not null comment ‘课程名称‘,
    -> tno int unique not null comment ‘教师编号‘
    -> )engine=innodb charset=utf8mb4;
Query OK, 0 rows affected (0.04 sec)

mysql> desc course;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| cno   | int(11)      | NO   | PRI | NULL    | auto_increment |
| cname | varchar(255) | NO   | UNI | NULL    |                |
| tno   | int(11)      | NO   | UNI | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

#成绩表
mysql>  create table score(
    ->  sno int  not null  comment ‘学号‘,
    ->  cno int  not null comment ‘课程编号‘,
    ->  score tinyint(3) unsigned zerofill not null comment ‘学生成绩‘
    ->  )engine=innodb charset=utf8mb4;
Query OK, 0 rows affected (0.05 sec)

mysql> desc score;
+-------+------------------------------+------+-----+---------+----------------+
| Field | Type                         | Null | Key | Default | Extra          |
+-------+------------------------------+------+-----+---------+----------------+
| sno   | int(11)                      | NO   |     | NULL    | auto_increment |
| cno   | int(11)                      | NO   |     | NULL    |                |
| score | tinyint(3) unsigned zerofill | NO   |     | NULL    |                |
+-------+------------------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

#学生表插入数据
mysql> INSERT INTO student(sno,sname,sage,ssex)
    -> VALUES
    -> (1,‘zhang3‘,18,‘m‘),
    -> (2,‘zhang4‘,18,‘m‘),
    -> (3,‘li4‘,18,‘m‘),
    -> (4,‘wang5‘,19,‘f‘),
    -> (5,‘zh4‘,18,‘m‘),
    -> (6,‘zhao4‘,18,‘m‘),
    -> (7,‘ma6‘,19,‘f‘);
Query OK, 7 rows affected (0.00 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> select sno,sname,sage,ssex from student;
+-----+--------+------+------+
| sno | sname  | sage | ssex |
+-----+--------+------+------+
|   1 | zhang3 |  018 | m    |
|   2 | zhang4 |  018 | m    |
|   3 | li4    |  018 | m    |
|   4 | wang5  |  019 | f    |
|   5 | zh4    |  018 | m    |
|   6 | zhao4  |  018 | m    |
|   7 | ma6    |  019 | f    |
+-----+--------+------+------+
7 rows in set (0.00 sec)

mysql> INSERT INTO student(sname,sage,ssex)
    -> VALUES
    -> (‘oldboy‘,20,‘m‘),
    -> (‘oldgirl‘,20,‘f‘),
    -> (‘oldp‘,25,‘m‘);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select sno,sname,sage,ssex from student;
+-----+---------+------+------+
| sno | sname   | sage | ssex |
+-----+---------+------+------+
|   1 | zhang3  |  018 | m    |
|   2 | zhang4  |  018 | m    |
|   3 | li4     |  018 | m    |
|   4 | wang5   |  019 | f    |
|   5 | zh4     |  018 | m    |
|   6 | zhao4   |  018 | m    |
|   7 | ma6     |  019 | f    |
|   8 | oldboy  |  020 | m    |
|   9 | oldgirl |  020 | f    |
|  10 | oldp    |  025 | m    |
+-----+---------+------+------+
10 rows in set (0.00 sec)

#教师表插入数据
mysql> INSERT INTO teacher(tno,tname) VALUES
    -> (101,‘oldboy‘),
    -> (102,‘hesw‘),
    -> (103,‘oldguo‘);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select tno,tname from teacher;
+-----+--------+
| tno | tname  |
+-----+--------+
| 101 | oldboy |
| 102 | hesw   |
| 103 | oldguo |
+-----+--------+
3 rows in set (0.00 sec)

#课程表插入数据
mysql> INSERT INTO course(cno,cname,tno)
    -> VALUES
    -> (1001,‘linux‘,101),
    -> (1002,‘python‘,102),
    -> (1003,‘mysql‘,103);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select cno,cname,tno from course;
+------+--------+-----+
| cno  | cname  | tno |
+------+--------+-----+
| 1001 | linux  | 101 |
| 1002 | python | 102 |
| 1003 | mysql  | 103 |
+------+--------+-----+
3 rows in set (0.00 sec)

#成绩表插入数据
mysql> INSERT INTO score(sno,cno,score)
    -> VALUES
    -> (1,1001,80),
    -> (1,1002,59),
    -> (2,1002,90),
    -> (2,1003,100),
    -> (3,1001,99),
    -> (3,1003,40),
    -> (4,1001,79),
    -> (4,1002,61),
    -> (4,1003,99),
    -> (5,1003,40),
    -> (6,1001,89),
    -> (6,1003,77),
    -> (7,1001,67),
    -> (7,1003,82),
    -> (8,1001,70),
    -> (9,1003,80),
    -> (10,1003,96);
Query OK, 17 rows affected (0.01 sec)
Records: 17  Duplicates: 0  Warnings: 0

mysql> select sno,cno,score from score;
+-----+------+-------+
| sno | cno  | score |
+-----+------+-------+
|   1 | 1001 |   080 |
|   1 | 1002 |   059 |
|   2 | 1002 |   090 |
|   2 | 1003 |   100 |
|   3 | 1001 |   099 |
|   3 | 1003 |   040 |
|   4 | 1001 |   079 |
|   4 | 1002 |   061 |
|   4 | 1003 |   099 |
|   5 | 1003 |   040 |
|   6 | 1001 |   089 |
|   6 | 1003 |   077 |
|   7 | 1001 |   067 |
|   7 | 1003 |   082 |
|   8 | 1001 |   070 |
|   9 | 1003 |   080 |
|  10 | 1003 |   096 |
+-----+------+-------+
17 rows in set (0.00 sec)