Establishment, modification and deletion of experiment table 1

Table of contents

1. Level 1: Create a table 

1.1 Task description

1.2 SQL statement

2. Level 2: Modify the table structure

2.1 Task description

2.2 SQL statements

3. Level 3: Delete table

3.1 Task description

3.2 SQL statement

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Data structure description (ie table structure)

1. Level 1: Create a table 

1.1 Task description

Use the create table statement in the SQL language to create Student, Course, and SC tables.

1.2 SQL statement

CREATE TABLE Student(
    Sno     char(10) PRIMARY KEY,
    Sname   varchar(20),
    Ssex    char(2),
    Sage    smallint,
    Sdept   varchar(20)
);

CREATE TABLE Course(
    Cno     char(10) PRIMARY KEY,
    Cname   varchar(20),
    Cpno    char(10),
    Ccredit smallint
);

CREATE TABLE SC(
    Sno     char(10),
    Cno     char(10),
    Grade   smallint,
    PRIMARY KEY(Sno,Cno)
);

2. Level 2: Modify the table structure

2.1 Task description

Use the alter table statement in the SQL statement to modify the table structure:

1. Add a column ( lowercase column name ) to the Student table: phone char(12);

2. Delete the Cpno column in the Course table;

3. Change the sdept column of the Student table to: sdept varchar(30).

2.2 SQL statements

ALTER TABLE Student ADD phone char(12);

ALTER TABLE Course DROP COLUMN Cpno;

ALTER TABLE Student ADD phone char(12);

3. Level 3: Delete table

3.1 Task description

Use the Drop table statement in the SQL statement to delete the table structure:

Delete the Student, Course and SC tables. (The SC table has external codes, please pay attention to the order of deletion)

3.2 SQL statement

DROP TABLE SC;--有外码的表优先被删除
DROP TABLE Student;
DROP TABLE Course;