编辑代码

CREATE DATABASE bookdb;
use bookdb;
CREATE TABLE book (
	bid int,
	bname varchar(255),
	author varchar(255),
	price double,
    publisher varchar(255),
    discount double,
    cid int
);

INSERT INTO book VALUES (1, '中国时代', '石永刚', 39.0,'作家出版社',27.8,1);
INSERT INTO book VALUES (2, '大国工匠',  '于万夫',76.0, '石油工业出版社',71,1);
INSERT INTO book VALUES (3, '给孩子的科技史',  '吴军', 69.0,'中信出版社',49,2);
INSERT INTO book VALUES (4, '故乡的泥土（全二册）',  '章云天', 98.0,'作家出版社',98,4);
INSERT INTO book VALUES (5, '老人与海',  '李四家隔壁',66, '北京时代化文书局',76,3);
INSERT INTO book VALUES (6, '舒克贝塔传',  '赵六家隔壁',55, '浙江少年儿童出版社',54,6);
INSERT INTO book VALUES (7, '漫画中国第一季（全书册）',  '上海印象', 76,'北方妇女儿童出版社',118,3);
 CREATE TABLE b_order(
     uid int,
     bid int,
     ordernum int,
     orderdate varchar(255)
 );
 INSERT INTO b_order VALUES(1001,1,2,'2020-03-12');
 INSERT INTO b_order VALUES(1001,3,1,'2020-04-15');
 INSERT INTO b_order VALUES(1001,1,1,'2020-09-15');
 INSERT INTO b_order VALUES(1003,7,1,'2009-12-14');
 INSERT INTO b_order VALUES(1003,3,1,'2020-10-10');
 INSERT INTO b_order VALUES(1005,5,1,'2009-08-17');
 INSERT INTO b_order VALUES(1006,5,1,'2020-09-01');
 INSERT INTO b_order VALUES(1006,1,2,'2020-10-21');
INSERT INTO b_order VALUES(1006,7,2,'2020-12-03');
SELECT bname,price

FROM book 
ORDER BY price DESC;
SELECT bname,price
FROM book
ORDER BY price DESC
LIMIT 3;
SELECT *
FROM b_order
WHERE orderdate='2020-10';
SELECT  DISTINCT ordernum
FROM  b_order;