2019-05-16 DDL

一、数据库

1.创建数据库

CREATE DATABASE BOOKS;
CREATE DATABASE IF NOT EXISTS BOOKS;

2.删除数据库

DROP DATABASE BOOKS;
DROP DATABASE IF EXISTS BOOKS;

二、表

1.创建表

CREATE TABLE JOB_GRADES(
    GRADE_LEVEL VARCHAR(3),
    LOWEST_SAL  INT,
    HIGHEST_SAL INT);

2.修改表

①.修改列名

ALTER TABLE BOOK CHANGE COLUMN PUBLISHDATE PUBDATE DATETIME 

②.修改列的类型或约束

ALTER TABLE BOOK MODIFY COLUMN PUBDATE TIMESTAMP;

③.新增列

ALTER TABLE AUTHOR ADD COLUMN ANNUAL DOUBLE;

④.删除列

ALTER TABLE AUTHOR DROP COLUMN ANNUAL;

⑤.修改表名

ALTER TABLE AUTHOR RENAME TO AUTHORR

3.删除表

DROP TABLE IF EXISTS BOOK_AUTHOR；

4.复制表

CREATE TABLE COPY LIKE AUTHOR; -- 仅仅复制表结构
CREATE TABLE COPY1 SELECT * FROM AUTHOR; -- 复制表的结构+数据
CREATE TABLE COPY3 SELECT ID,AU_NAME FROM AUTHOR WHERER NATION = ''; -- 只复制部分数据