SQL开发知识:Mysql多层子查询示例代码

用户表

create table if not exists tb_book (
book_id char(10) not null comment ‘book主键’,
book_name char(30) not null comment ‘书名’,
book_type char(10) not null comment ‘类别’,
book_brief varchar(500) not null comment ‘简介’,
book_online_time timestamp not null comment ‘上线时间’,
book_author char(20) not null comment ‘作者’,
book_grade int(2) not null comment ‘评分’,
book_word_number int(5) not null comment ‘售量’,
book_small_picture char(100) not null comment ‘书小图’,
book_big_picture char(100) comment ‘书大图’,
primary key (book_id)
)
replace into tb_user(user_id,user_name,email,phone_number,balance,briefs,birthday,grade,password,avatar,signature) values
(‘324123125′,’llx’,’1753552134@qq.com’,’17665621006′,0,’风一样的少年’,CURDATE(),25,’123456′,’default.png’,’我就是我,不一样的烟火’),
(‘324223125′,’user2345′,’2341235@qq.com’,’13722211122′,0,’风一样的少年’,CURDATE(),25,’123456′,’default.png’,’不顾别人感受是自私,太顾别人感受是自虐。’),
(‘324423125′,’ling’,’234125@qq.com’,’13351234112′,0,’风一样的少年’,CURDATE(),25,’123456′,’default.png’,’年龄永远不是衡量一个人的刻度,只有责任的叠加才会让人逐渐成长。’),
(‘324623125′,’xz’,’2341235@qq.com’,’15534562345′,0,’风一样的少年’,CURDATE(),25,’123456′,’default.png’,’昨天再好,也走不回去;明天再难,也要抬脚继续。’);
select * from tb_user

图书表

create table if not exists tb_book (
book_id char(10) not null comment ‘book主键’,
book_name char(30) not null comment ‘书名’,
book_type char(10) not null comment ‘类别’,
book_brief varchar(500) not null comment ‘简介’,
book_online_time timestamp not null comment ‘上线时间’,
book_author char(20) not null comment ‘作者’,
book_grade int(2) not null comment ‘评分’,
book_word_number int(5) not null comment ‘售量’,
book_small_picture char(100) not null comment ‘书小图’,
book_big_picture char(100) comment ‘书大图’,
primary key (book_id)
)
insert into tb_book(book_id, book_name, book_type, book_brief, book_online_time, book_author, book_grade,
book_word_number, book_small_picture, book_big_picture)
values (‘0000000001’, ‘天降鬼才’, ‘玄幻’,
‘我不会奇门遁甲,也不懂风水八卦,但江湖人都称我绝世鬼才。为什么?因为我脑子有坑!装满来至新世纪的现代学识!讲道理,其实我是个很纯洁的斯文人,不管你们信不信,反正我是信了。’, now(), ‘武异’, 10, 1,
‘0000000001.png’, ‘0000000001.png’),
(‘0000000002’, ‘暴君的穿越小邪后’, ‘古代言情’,
‘一名现代A帮千金,机缘巧合下穿越到大齐——一个历史上完全不存在的朝代,在这个波诡云谲的时代,看她如何见招拆招,并和那个冷面帝王谈一场千古绝恋。带着皇帝在现代吃喝玩乐,在古代又玩起了帝后和鸣,好不快活!’,
now(), ‘非墨千泷’, 10, 1412342, ‘0000000002.png’, ‘0000000002.png’),
(‘0000000003’, ‘汗灵昭烈’, ‘武侠仙侠’,
‘打虎上山,行侠入世,一代英雄聚念而生。单臂挚天,双剑仗义,千年华夏因义流芳。武松是谁?他为何而来?他又将为谁而战?一代汉灵入世,沧海下暗流涌动,乾坤里谁是英雄!’,
now(), ‘千秋一梦’, 10, 151241, ‘0000000003.png’, ‘0000000003.png’),
(‘0000000004’, ‘大明烟火’, ‘历史军事’, ‘朱元璋:“一群贪赃枉法之辈,朕要杀光他们。”韩度:“陛下息怒,与其杀了,不如废物利用,压榨干净他们的剩余价值才好。”朱元璋:……’, now(),
‘阳光下写字’, 10, 1123424, ‘0000000004.png’, ‘0000000004.png’),
(‘0000000005’, ‘重生八零甜妻有点狂’, ‘都市言情’,
‘眼睛一闭一睁,乐薇重回十六岁。白手起家打拼出的跨国集团没了,上亿身家也没了,只有家徒四壁和兜里的几毛钱,还有她的小学学历。重活一回,除了赚钱,她还要走进知识殿堂,成为学霸,走向巅峰,出任CEO,迎娶白富美!一身戎装又帅又飒的小柳同志疑惑:谁是白富美?又白又富又美的乐大CEO理直气壮:你。’,
now(), ‘林间雪’, 10, 112341, ‘0000000005.png’, ‘0000000005.png’),
(‘0000000006’, ‘小道姑成仙记’, ‘玄幻’,
‘斩恶鬼,斗尸煞,收妖邪!杀魔人,寻仙草,炼仙丹!初出茅庐的郑小雅,为了救出师尊,重振师门,踏上了一条危险曲折,惊心动魄的道路一个又一一个不可思议的经历,在她的生命中演绎,。最后她发现,自己的命运原来一直都不掌握在自己的手中,且看她如何打破命运的枷锁,成就仙道之躯。’,
now(), ‘羊小乐’, 10, 112342, ‘0000000006.png’, ‘0000000006.png’),
(‘0000000007’, ‘满级游戏宅在兽世惹桃花’, ‘幻想时空’,
‘游戏玩家顾晓黎因为系统bug携带满级技能穿越到游戏中的兽人副本,踏上漫漫归家之路,却被各色美男拐骗,只得留下,发展城邦,与兽夫共同对抗恶势力。甜宠玛丽苏。’,
now(), ‘无摆’, 10, 15234, ‘0000000007.png’, ‘0000000007.png’)

收藏夹表

create table if not exists tb_collection(
collection_id char(11) not null comment ‘收藏id’,
book_id char(10) not null comment ‘book主键’,
user_id CHAR(16) NOT NULL COMMENT ‘用户id’,
collection_time timestamp not null comment ‘收藏时间’,
primary key (collection_id),
constraint `collection_book` foreign key (`book_id`) references `tb_book`(`book_id`),
constraint `collection_user` foreign key (`user_id`) references `tb_user`(`user_id`)
)
set foreign_key_checks = 0; # 暂时取消外键约束
insert into tb_collection(collection_id, book_id, user_id, collection_time)
values (‘00000000001’, ‘0000000001’, ‘324123125’, now()),
(‘00000000002’, ‘0000000002’, ‘324123125’, now()),
(‘00000000003’, ‘0000000003’, ‘324123125’, now()),
(‘00000000004’, ‘0000000004’, ‘324123125’, now());
set foreign_key_checks = 1; # 恢复外键约束

查询 思路:从根据用户id查询收藏夹表里的book_id,再用拿到的book_id查询图书

select *
from tb_book
where tb_book.book_id
in (select tb_collection.book_id
from tb_collection
where user_id = ‘324123125’)

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