【MySQL】SQL语句进阶-创建sql练习环境

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互联网老辛 2022-02-13 09:51:42 ©著作权

文章标签 sql练习环境 mysql 测试数据当前日期 文章分类 代码人生

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开始之前先来学习一个数据库查询命令

select

1）打印当前日期和时间

mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2020-11-28 12:34:56 |
+---------------------+
1 row in set

mysql>

2）打印当前日期

mysql> select curdate();
+------------+
| curdate()  |
+------------+
| 2020-11-28 |
+------------+
1 row in set

mysql>

3. 打印当前数据库

mysql> select database();
+------------+
| database() |
+------------+
| zmedu      |
+------------+
1 row in set

mysql>

4. 打印MySQL版本

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.22    |
+-----------+
1 row in set

5. 打印当前用户

mysql> select user();
+----------------+
| user()         |
+----------------+
| root@localhost |
+----------------+
1 row in set

6. 查看系统运行状态的信息

mysql> show global status like ‘Thread%’;

±------------------±------+

| Variable_name | Value |

±------------------±------+

| Threads_cached | 2 |

| Threads_connected | 1 |

| Threads_created | 3 |

| Threads_running | 2 |

±------------------±------+

4 rows in set

搭建练习环境

说明：

–1.学生表

Student(s_id,s_name,s_birth,s_sex) –学生编号,学生姓名, 出生年月,学生性别

–2.课程表

Course(c_id,c_name,t_id) – –课程编号, 课程名称, 教师编号

–3.教师表

Teacher(t_id,t_name) –教师编号,教师姓名

–4.成绩表

Score(s_id,c_id,s_score) –学生编号,课程编号,分数

建立学生表：

mysql> CREATE TABLE `Student`(
`s_id` VARCHAR(20),
`s_name` VARCHAR(20) NOT NULL DEFAULT '',
`s_birth` VARCHAR(20) NOT NULL DEFAULT '',
`s_sex` VARCHAR(10) NOT NULL DEFAULT '',
PRIMARY KEY(`s_id`)
);
Query OK, 0 rows affected

建立课程表

mysql> CREATE TABLE `Course`(
`c_id` VARCHAR(20),
`c_name` VARCHAR(20) NOT NULL DEFAULT '',
`t_id` VARCHAR(20) NOT NULL,
PRIMARY KEY(`c_id`)
);
Query OK, 0 rows affected

mysql>

建立教师表

mysql> CREATE TABLE `Teacher`(
`t_id` VARCHAR(20),
`t_name` VARCHAR(20) NOT NULL DEFAULT '',
PRIMARY KEY(`t_id`)
);
Query OK, 0 rows affected

建立成绩表

CREATE TABLE `Score`(
`s_id` VARCHAR(20),
`c_id` VARCHAR(20),
`s_score` INT(3),
PRIMARY KEY(`s_id`,`c_id`)
);

插入学生表测试数据：

insert into Student values('01' , '高胜寒' , '1990-06-01' , '男');
insert into Student values('02' , '高峰' , '1990-2-21' , '男');
insert into Student values('03' , '维度' , '1990-07-20' , '男');
insert into Student values('04' , '李云龙' , '1995-08-06' , '男');
insert into Student values('05' , '沐晨' , '1991-12-01' , '女');
insert into Student values('06' , '舒展' , '1992-03-01' , '女');
insert into Student values('07' , '李白' , '1989-07-01' , '女');
insert into Student values('08' , '白居易' , '1990-01-20' , '女');

插入课程表测试数据：

insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
insert into Course values('04' , '化学' , '04');

插入教师表数据

insert into Teacher values('01' , '张帅');
insert into Teacher values('02' , '李广');
insert into Teacher values('03' , '王浩');
insert into Teacher values('04' , '李强');

成绩表测试数据

insert into Score values('01' , '01' , 80);
insert into Score values('01' , '02' , 90);
insert into Score values('01' , '03' , 99);
insert into Score values('02' , '01' , 70);
insert into Score values('02' , '02' , 60);
insert into Score values('02' , '03' , 80);
insert into Score values('03' , '01' , 80);
insert into Score values('03' , '02' , 80);
insert into Score values('03' , '03' , 80);
insert into Score values('04' , '01' , 50);
insert into Score values('04' , '02' , 30);
insert into Score values('04' , '03' , 20);
insert into Score values('05' , '01' , 76);
insert into Score values('05' , '02' , 87);
insert into Score values('06' , '01' , 31);
insert into Score values('06' , '03' , 34);
insert into Score values('07' , '02' , 89);
insert into Score values('07' , '03' , 98);