MySql多表增删查改

#school 是否有school，有的话删除drop database if EXISTS school;#创建school数据库create database school;use school;#图书信息表 设定1001开始drop table if EXISTS books;create table books(bno int(4) not null primary key auto_increment,bname VARCHAR(20) not null,author VARCHAR(20),price float not null,quanitity int(4) not null)auto_increment=1001;#借书信息表 设定101开始drop table if EXISTS card;create table card(cno int(4) not null primary key auto_increment,name VARCHAR(20) not null unique,class VARCHAR(20) not null)auto_increment=101;#图书借阅信息表drop table if EXISTS info;create table info(id int(4) not null primary key auto_increment,cno int(4) REFERENCES card(cno),bno int(4) REFERENCES book(bno),rdate datetime);show tables;desc books;#表结构#插入图书数据booksinsert into books(bname,price,author,quanitity)values(\"红楼梦\",50,\"施耐庵\",30),(\"三国演义\",50,\"xxx\",20),(\"情商\",50,\"qqq\",10);select * from books;#插入借书信息表cardinsert into card(name,class) values(\"张三\",\"表演1班\"),(\"李四\",\"模特2班\"),(\"田七\",\"歌手1班\");select * from card;#插入借阅信息表infoinsert into info values(1,101,1001,NOW());insert into info values(2,102,1002,NOW());insert into info values(3,103,1003,NOW());select * from info;--修改update card set class=\"大数据1班\" where cno=101;--查询所有select * from books b,card c,info i where b.bno=i.bno and c.cno=i.cno;--删除delete from info where id=3;