示例及练习1-MOSHOU.hero.txtcreate database MOSHOU;use MOSHOU;create table hero(id int,name char(15),sex enum("男","女"),country char(10));insert into hero values(1,"曹操","男","魏国"),(2,"小乔","女","吴国"),(3,"诸葛亮","男","蜀国"),(4,"貂蝉","女","东汉"),(5,"赵子龙","男","蜀国"),(6,"张飞","男","蜀国");table:+------+-----------+------+---------+| id | name | sex | country |+------+-----------+------+---------+| 1 | 曹操 | 男 | 魏国 || 2 | 小乔 | 女 | 吴国 || 3 | 诸葛亮 | 男 | 蜀国 || 4 | 貂蝉 | 女 | 东汉 || 5 | 赵子龙 | 男 | 蜀国 || 6 | 张飞 | 男 | 蜀国 |+------+-----------+------+---------+1.查找所有蜀国人信息 select * from hero where country="蜀国"2.查找女英雄的信息,只显示姓名,性别和国家 select name,sex,country from hero where sex="女"3.把曹操的国籍改为蜀国 update hero set country="蜀国" where name="曹操";4.把张飞的性别改为女,国籍改为泰国 update hero set sex="女",country="泰国" where name="张飞";5.把id为2的记录的姓名改为司马懿,性别改为男,国家改为魏国 update hero set name="司马懿",sex="男",country="魏国" where id=2;6.删除所有泰国人 delete from hero where country="泰国";7.删除所有的英雄 delete from hero;==============================================2-MOSHOU.sanguo.txtuse MOSHOU;create table sanguo(id int,name char(20),gongji int,fangyu tinyint unsigned,sex enum("男","女"),country varchar(20));insert into sanguo values(1,"诸葛亮",120,20,"男","蜀国"),(2,"司马懿",119,25,"男","魏国"),(3,"关6羽",188,60,"男","蜀国"),(4,"赵云666",200,66,"男","魏国"),(5,"8孙权",110,20,"男","吴国"),(6,"貂蝉",666,10,"女","魏国"),(7,null,1000,99,"男","蜀国"),(8,"",1005,88,"女","蜀国");table:+------+-----------+--------+--------+------+---------+| id | name | gongji | fangyu | sex | country |+------+-----------+--------+--------+------+---------+| 1 | 诸葛亮 | 120 | 20 | 男 | 蜀国 || 2 | 司马懿 | 119 | 25 | 男 | 魏国 || 3 | 关6羽 | 188 | 60 | 男 | 蜀国 || 4 | 赵云666 | 200 | 66 | 男 | 魏国 || 5 | 8孙权 | 100 | 60 | 男 | 吴国 || 6 | 貂蝉 | 666 | 10 | 女 | 魏国 || 7 | NULL | 1000 | 99 | 男 | 蜀国 || 8 | | 1005 | 88 | 女 | 蜀国 |+------+-----------+--------+--------+------+---------+===========================================================1.找出攻击力高于150的英雄的名字和攻击力select name,gongji from sanguo where gongji>150;2.找出防御力不等于100的英雄信息select * from sanguo where fangyu!=100;3.找出攻击力大于200的蜀国英雄的名字和攻击力select name,gongji from sanguo where country="蜀国" and gongji>200;4.查找蜀国和魏国的英雄信息select * from sanguo where country in ("蜀国","魏国");5.将吴国英雄中攻击值为110的英雄的攻击值设置为100,防御值设置为60update sanguo set gongji=100,fangyu=60 where country="吴国" and gongji=110;6.查找攻击值在100-200之间的蜀国英雄信息select * from sanguo where country="蜀国" and (gongji between 100 and 200);7.查找除去蜀国和吴国的女英雄信息select * from sanguo where country not in("蜀国","吴国") and sex="女";8.查找(id为1,3,5的蜀国英雄和貂蝉) 的编号,姓名,国家select id,name,country from sanguo where name="貂蝉" or (country="蜀国" and id in (1,3,5) );9.查找姓名为null的蜀国男英雄信息select * from sanguo where name is null and country="蜀国" and sex="男";10.查找姓名为""的英雄的id,姓名,国家select id,name,country from sanguo where name="";11.将英雄的按防御值从低到高排序select * from sanguo order by fangyu;12.将蜀国英雄按攻击值从高到低排序select * from sanguo where country="蜀国" order by gongji desc;13.将魏蜀两国的男英雄中名字为三个字的英雄按防御值升序排列select * from sanguo where country in ("魏国","蜀国") and sex="男" and name like "___" order by fangyu;14.查找防御值第2名到第4名的蜀国英雄记录select * from sanguo where country="蜀国" order by fangyu desc limit 1,3;15.查找攻击值前三名且名字不为空值的蜀国英雄的记录select * from sanguo where country="蜀国" and name is not null order by gongji desc limit 3;16.攻击力最强值是多少select max(gongji) as best from sanguo; 用best取代max(gongji)在表格内显示字段名17.统计id,name两个字段分别有多少条记录select count(id),count(name) from sanguo; count不统计null,统计""18.统计蜀国英雄中攻击值大于200的英雄数量select count(*) as "蜀国攻击力>200的英雄数量" from sanguo where country="蜀国" and gongji>200;19.统计sanguo表中一共有几个国家select country from sanguo group by country;select distinct country from sanguo; distinct的实现select distinct name,country from sanguo; 这句把name,country当成整体,记录必须完全一样才能去重,distinct后面可以跟n个字段20.计算所有国家的平均攻击力select country,avg(gongji) from sanguo group by country;21.查找所有国家中 英雄数量最多的 前2名国家名称及英雄数量select country,count(*) as "numbers(英雄)" from sanguo group by country order by count(*) desc limit 2;22.找出平均攻击力大于105的国家的前2名,显示国家名称和平均攻击力select country,avg(gongji) as "平均攻击力" from sanguo group by country having avg(gongji)>105 order by avg(gongji) desc limit 2;23.计算蜀国一共有多少个英雄select count(distinct name) from sanguo where country="蜀国";24.查询时显示所有英雄的攻击力 * 10select name,gongji*10,country from sanguo;25找出每个国家攻击力最高的英雄的名字和攻击值(子查询)select name,gongji from sanguo where (country,gongji) in(select country,max(gongji) from sanguo group by country);==================================================示例3table province+----+--------+-----------+| id | pid | pname |+----+--------+-----------+| 1 | 130000 | 河北省 || 2 | 140000 | 陕西省 || 3 | 150000 | 四川省 || 4 | 160000 | 广东省 || 5 | 170000 | 山东省 || 6 | 180000 | 湖北省 || 7 | 190000 | 河南省 || 8 | 200000 | 海南省 || 9 | 200001 | 云南省 || 10 | 200002 | 山西省 |+----+--------+-----------+table city+----+--------+--------------+--------+| id | cid | cname | cp_id |+----+--------+--------------+--------+| 1 | 131100 | 石家庄市 | 130000 || 2 | 131101 | 沧州市 | 130000 || 3 | 131102 | 廊坊市 | 130000 || 4 | 131103 | 西安市 | 140000 || 5 | 131104 | 成都市 | 150000 || 6 | 131105 | 重庆市 | 150000 || 7 | 131106 | 广州市 | 160000 || 8 | 131107 | 济南市 | 170000 || 9 | 131108 | 武汉市 | 180000 || 10 | 131109 | 郑州市 | 190000 || 11 | 131110 | 北京市 | 320000 || 12 | 131111 | 天津市 | 320000 || 13 | 131112 | 上海市 | 320000 || 14 | 131113 | 哈尔滨 | 320001 || 15 | 131114 | 雄安新区 | 320002 |+----+--------+--------------+--------+table county+----+--------+--------------+--------+| id | coid | coname | copid |+----+--------+--------------+--------+| 1 | 132100 | 正定县 | 131100 || 2 | 132102 | 浦东新区 | 131112 || 3 | 132103 | 武昌区 | 131108 || 4 | 132104 | 哈哈 | 131115 || 5 | 132105 | 安新县 | 131114 || 6 | 132106 | 容城县 | 131114 || 7 | 132107 | 雄县 | 131114 || 8 | 132108 | 嘎嘎 | 131115 |+----+--------+--------------+--------+3.1.内连接 1.从省表和市表中提取省名和市名一一对应 select province.pname,city.cname from province inner join city on province.pid = city.cp_id; #只显示完全匹配的值 2.从省市县表中提取省市县名一一对应 select province.pname,city.cname,county.coname from province inner join city on province.pid = city.cp_id inner join county on county.copid = city.cid; #连接的是前面生成的结果集 3.用左连接以省表为主显示省市详细信息 select province.pname,city.cname from province left join city on province.pid = city.cp_id; #省表显示所有,匹配的市表有显示,未匹配显示null 4.用左连接以省表为主显示省市县详细信息 select province.pname,city.cname,county.coname from province left join city on province.pid = city.cp_id left join county on county.copid = city.cid; 5.显示省市县详细信息,要求县全部显示 select province.pname,city.cname,county.coname from province left join city on province.pid = city.cp_id right join county on county.copid = city.cid; 6.显示省市区详细信息,要求 市 全部显示 select province.pname,city.cname,county.coname from province right join city on province.pid = city.cp_id left join county on county.copid = city.cid;
来源：https://www.cnblogs.com/huohu121/p/12300457.html