CentOS MySQL语句入门
Posted 白菜素三鲜丶
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mysql语句入门
MySQL的连接管理
自带的连接工具（客户端）
- mysql
-u:user指定MySQL的用户
-p:password指定MySQL用户的密码
-S:socket指定socket文件的位置
-h:host指定主机IP地址
-e:exec执行SQL语句
-p:port指定端口
--protocol=name:指定连接方式- mysqladmin
- mysqldump（逻辑备份）
第三方连接工具（客户端）
- Navicat
- SQLmanager
- SQLyog
MySQL启动关闭流程
启动
/etc/init.d/mysqld start
systemctl start mysqld
mysqld_safe --选项关闭
/etc/init.d/mysqld stop
systemctl stop mysqld
mysqladmin -uroot -S /data/3309/data/3309.sock shutdown
------------------------------------------------------
kill -9 pid ?
killall mysqld ?
pkill mysqld ?
## 不到万不得已不要使用上面三个命令，非要用的话建议使用pkill mysqldMySQL实例初始化配置
- 预编译
- 命令行
- 配置文件（读取顺序）
- /etc/my.cnf
- /etc/mysql/my.cnf
- $basedir/my.cnf
- --defaults-extra-file=/opt/my.cnf
- ~/.my.cnf
优先级
~/.my.cnf > --defaults-extra-file=/opt/my.cnf > $basedir/my.cnf > /etc/mysql/my.cnf >
/etc/my.cnf
注意：如果启动MySQL加了--defaults-file=/etc/my.cnf选项，其它位置的配置文件都不读取
思考
#cmake：
socket=/application/mysql/tmp/mysql.sock
#命令行：
--socket=/tmp/mysql.sock
#配置文件：
/etc/my.cnf中[mysqld]标签下：socket=/opt/mysql.sock
#default参数：
--defaults-file=/tmp/a.txt配置文件中[mysqld]标签下：socket=/tmp/test.sock
/application/mysql/tmp/mysql.sock
/tmp/mysql.sock
/opt/mysql.sock
/tmp/test.sock
mysqld --defaults-file=/tmp/a.txt --socket=/tmp/mysql.sock
/tmp/mysql.sock
## 结论
默认配置，优先级
1.命令行
2.配置文件
- ~/.my.cnf
- --defaults-extra-file=/opt/my.cnf
- $basedir/my.cnf
- /etc/mysql/my.cnf
- /etc/my.cnf
3.编译参数初始化配置的作用
- 影响服务端的启动
- 影响到客户端的连接
[mysqld] [server] ## 这两个标签下的配置，都是来影响服务端启动的
[mysql][mysqladmin][mysqldump] ## 这几个标签，影响对应的客户端命令
[client] ## 这个标签，影响所有的客户端命令
## 注意：修改客户端配置，不需要重启mysql，修改服务端配置[mysqld]需要重启mysql
[mysqld]
skip_name_resolve
basedir=/application/mysql
datadir=/application/mysql/data
server_id=10
socket=/opt/mysql.sock
[client]
user=root
password=abc
socket=/opt/mysql.sockMySQL的SQL语句
客户端管理
- mysql
## 查看命令帮助
? \\? help \\h
## 查看状态
status \\s
## 退出
exit quit \\q
## 结束当前的SQL语句
\\c
## Ctrl + c
MySQL5.6中：退出MySQL
MySQL5.7中：结束当前SQL语句，类似于\\c
## 在MySQL中执行系统命令
system \\!
## 临时将操作记录到指定的文件中
tee \\T
tee /tmp/mysql.log
\\T /tmp/mysql.log
## 切换数据库
use \\u
use mysql
\\u mysql
## 导入数据
source \\.
source /tmp/zls.sql
\\. /tmp/zls.sql
## 格式化（key:value）方式，显示数据
\\G
mysql> select * from mysql.user\\G
### 客户端配置，显示当前所在数据库及登录用户
[client]
prompt="\\u@\\h:\\d>"- mysqladmin
mysqladmin password 密码 # 修改密码或者设置密码
mysqladmin shutdown # 关闭mysql服务
mysqladmin ping # 检测MySQL是否存活
mysqladmin status # 查看MySQL的状态
mysqladmin variables # 查看MySQL的默认配置（内置变量）
mysqladmin create 库名 # 在库外创建数据库
mysqladmin drop 库名 # 在库外删除数据库
mysqladmin reload # 重新加载数据库
mysqladmin flush-log # 刷新授权表
## 注意有密码:-u -pSQL层的SQL语句
什么是SQL语句
结构化的查询语句 标准：SQL-92
SQL语句的分类
DDL
Database Definition Language
数据 定义 语言
# 开发规范：
(01) 表名不能大写,数字开头,16个字符串
(02) 表名和业务有关
(03) drop 语句禁止
(04) 选择合适的数据类型
(05) 必须要有主键
(06) 列尽量非空约束
(07) 减少外键约束
(08) 必须设置存储引擎和字符集
(09) 列必须要有注释
(10) 对于非负数设置数据类型约束--无符号
库
# 增
语法：
Syntax:
CREATE DATABASE | SCHEMA [IF NOT EXISTS] db_name
[create_option] ...
create_option: [DEFAULT]
CHARACTER SET [=] charset_name
| COLLATE [=] collation_name
create database 库名;
create schema 库名;
create database 库名 character set utf8;
create database 库名 charset utf8;
create database if not exists 库名 charset utf8 collate utf8_bin;
# 删
drop database 库名;
# 改
修改字符集
alter database www charset latin1;
#### DQL查看数据库的字符集
show create database www;
+----------+----------------------------------------------------------------+
| Database | Create Database |
+----------+----------------------------------------------------------------+
| www | CREATE DATABASE `www` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+----------------------------------------------------------------+表
# 增
create table 表名(字段1 数据类型 约束,字段 数据类型 约束....)
建表，至少要给的是 字段名称和数据类型
create table www.student(id int not null primary key auto_increment,name varchar(10),ageage tinyint,gender enum(0,1));
### 简洁方式
mysql> create table www.student2(
-> id int,
-> name varchar(10),
-> age tinyint,
-> gender enum(0,1));
Query OK, 0 rows affected (0.02 sec)
mysql> desc student2;
+--------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(10) | YES | | NULL | |
| age | tinyint(4) | YES | | NULL | |
| gender | enum(0,1) | YES | | NULL | |
+--------+---------------+------+-----+---------+-------+
## 数据类型
int： 整数 -2^31 ~ 2^31 -1
varchar：字符类型 （变长）
char： 字符类型 （定长）
smallint: 较小整数数据类型（-2^15到2^15-1）
mediumint: 中型整数数据类型
bigint: 较大整数数据类型（-2^63到2^63-1）
float: 浮点数（小型单精度四个字节浮点数）
double:常规双精度（八个字节浮点数）
decimal:定点数（包含整数部分，小鼠部分或同事包括两者的精确值数值）
bit:位字段值
tinyint
enum
datetime
timestamp
# 最多输入十个字符
name varchar(10)
# 占据十个字符
name char(10)
# 只能输入11位的字符
phone char(11)
tinyint： 整数 -128 ~ 127
enum： 枚举类型
enum(A,B,C,D)
datetime： 时间类型 年月日时分秒
## 约束
not null： 非空
primary key： 主键（唯一且非空的）一张表只能有一个主键
auto_increment： 自增（此列必须是：primary key或者unique key）
unique key： 唯一键，单独的唯一的 唯一键 + not null
default： 默认值
unsigned： 无符号（非负）
comment： 注释
# 删
mysql> drop table student2;
## 删除用户
mysql> drop user wsh1@localhost;
# 改
## 修改表名
mysql> show tables;
+---------------+
| Tables_in_www |
+---------------+
| student3 |
+---------------+
1 row in set (0.00 sec)
mysql> alter table student3 rename stu;
Query OK, 0 rows affected (0.12 sec)
mysql> show tables;
+---------------+
| Tables_in_www |
+---------------+
| stu |
+---------------+
1 row in set (0.00 sec)
## 添加字段(将字段添加在表的最后一列)
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
+--------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
mysql> alter table stu add done varchar(10) not null;
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
+--------+---------------------+------+-----+---------+----------------+
7 rows in set (0.00 sec)
mysql> alter table stu add wsh char(5) default 3; ## 带默认值添加字段
Query OK, 0 rows affected (0.14 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
| wsh | char(5) | YES | | 3 | |
+--------+---------------------+------+-----+---------+----------------+
8 rows in set (0.00 sec)
## 添加多个字段
mysql> alter table stu add www int(4),add qq char(11) not null;
Query OK, 0 rows affected (0.15 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
| wsh | char(5) | YES | | 3 | |
| www | int(4) | YES | | NULL | |
| qq | char(11) | NO | | NULL | |
+--------+---------------------+------+-----+---------+----------------+
10 rows in set (0.00 sec)
## 按指定位置添加字段
mysql> alter table stu add tt char(2) after age；
Query OK, 0 rows affected (0.14 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| tt | char(2) | YES | | NULL | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
| wsh | char(5) | YES | | 3 | |
| www | int(4) | YES | | NULL | |
| qq | char(11) | NO | | NULL | |
+--------+---------------------+------+-----+---------+----------------+
11 rows in set (0.00 sec)
## 将字段添加在最前面一列
mysql> alter table stu add ee int(3) first;
Query OK, 0 rows affected (0.15 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| ee | int(3) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| tt | char(2) | YES | | NULL | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
| wsh | char(5) | YES | | 3 | |
| www | int(4) | YES | | NULL | |
| qq | char(11) | NO | | NULL | |
+--------+---------------------+------+-----+---------+----------------+
12 rows in set (0.00 sec)
## 删除字段
mysql> alter table stu drop qq;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table stu drop www;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| ee | int(3) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| tt | char(2) | YES | | NULL | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
| wsh | char(5) | YES | | 3 | |
+--------+---------------------+------+-----+---------+----------------+
10 rows in set (0.00 sec)
## 修改数据类型和属性
mysql> alter table stu change ee er char(12);
Query OK, 5 rows affected (0.06 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| er | char(12) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| tt | char(2) | YES | | NULL | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
| done | varchar(10) | NO | | NULL | |
| wsh | char(5) | YES | | 3 | |
+--------+---------------------+------+-----+---------+----------------+
10 rows in set (0.00 sec)DML
Data Manipulation Language
数据 操作 语言
所有的DML都是操作表内容的
## 增
# 插入单条数据
mysql> desc stu;
+--------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(3) unsigned | NO | | 18 | |
| gender | enum(0,1) | NO | | 1 | |
| phone | char(11) | YES | | NULL | |
| bir | datetime | NO | | NULL | |
+--------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
mysql> insert into stu(name,age,gender,phone,bir) value(wsh,22,1,133,19900805);
Query OK, 1 row affected (0.00 sec)
mysql> select * from stu;
+----+----------+-----+--------+-------------+---------------------+
| id | name | age | gender | phone | bir |
+----+----------+-----+--------+-------------+---------------------+
| 1 | zhangsan | 18 | 0 | NULL | 0000-00-00 00:00:00 |
| 2 | lisi | 22 | 1 | NULL | 0000-00-00 00:00:00 |
| 3 | zhaoliu | 38 | 0 | NULL | 0000-00-00 00:00:00 |
| 4 | qianqi | 44 | 1 | NULL | 0000-00-00 00:00:00 |
| 5 | zhuba | 55 | 1 | 15858170920 | 1995-09-09 00:00:00 |
| 6 | wangwu | 33 | 1 | 133 | 1722-05-06 00:00:00 |
| 7 | wsh | 22 | 1 | 133 | 1990-08-05 00:00:00 |
+----+----------+-----+--------+-------------+---------------------+
7 rows in set (0.00 sec)
# 插入多条数据(默认字段可不加)
mysql> insert into stu(name,age,gender,phone,bir)
-> value(qiqi,33,0,153,19960506),
-> (wuwu,25,1,666,20000605);
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from stu;
+----+----------+-----+--------+-------------+---------------------+
| id | name | age | gender | phone | bir |
+----+----------+-----+--------+-------------+---------------------+
| 1 | zhangsan | 18 | 0 | NULL | 0000-00-00 00:00:00 |
| 2 | lisi | 22 | 1 | NULL | 0000-00-00 00:00:00 |
| 3 | zhaoliu | 38 | 0 | NULL | 0000-00-00 00:00:00 |
| 4 | qianqi | 44 | 1 | NULL | 0000-00-00 00:00:00 |
| 5 | zhuba | 55 | 1 | 15858170920 | 1995-09-09 00:00:00 |
| 6 | wangwu | 33 | 1 | 133 | 1722-05-06 00:00:00 |
| 7 | wsh | 22 | 1 | 133 | 1990-08-05 00:00:00 |
| 8 | wsh | 22 | 1 | 133 | 1990-08-05 00:00:00 |
| 9 | qiqi | 33 | 0 | 153 | 1996-05-06 00:00:00 |
| 10 | wuwu | 25 | 1 | 666 | 2000-06-05 00:00:00 |
+----+----------+-----+--------+-------------+---------------------+
10 rows in set (0.00 sec)
## 删(危险)
使用delete一定要加条件
mysql> delete from stu; (不要这么删除)
# 加条件
mysql> delete from stu where id=10;
Query OK, 1 row affected (0.02 sec)
mysql> select * from stu;
+----+----------+-----+--------+-------------+---------------------+
| id | name | age | gender | phone | bir |
+----+----------+-----+--------+-------------+---------------------+
| 1 | zhangsan | 18 | 0 | NULL | 0000-00-00 00:00:00 |
| 2 | lisi | 22 | 1 | NULL | 0000-00-00 00:00:00 |
| 3 | zhaoliu | 38 | 0 | NULL | 0000-00-00 00:00:00 |
| 4 | qianqi | 44 | 1 | NULL | 0000-00-00 00:00:00 |
| 5 | zhuba | 55 | 1 | 15858170920 | 1995-09-09 00:00:00 |
| 6 | wangwu | 33 | 1 | 133 | 1722-05-06 00:00:00 |
| 7 | wsh | 22 | 1 | 133 | 1990-08-05 00:00:00 |
| 8 | wsh | 22 | 1 | 133 | 1990-08-05 00:00:00 |
| 9 | qiqi | 33 | 0 | 153 | 1996-05-06 00:00:00 |
+----+----------+-----+--------+-------------+---------------------+
9 rows in set (0.00 sec)
# 想全部删除也要加条件
mysql> delete from stu where 1=1;
Query OK, 9 rows affected (0.00 sec)
mysql> select * from stu;
Empty set (0.00 sec)
## 注意：一般在删除数据时，我们会根据唯一性的字段，进行删除
delete from mysql.user where user=wsh and host=localhost;
## 改
使用update一定要加条件
mysql> select * from stu;
+----+------+-----+--------+-------+---------------------+
| id | name | age | gender | phone | bir |
+----+------+-----+--------+-------+---------------------+
| 11 | qiqi | 33 | 0 | 153 | 1996-05-06 00:00:00 |
| 12 | wuwu | 25 | 1 | 666 | 2000-06-05 00:00:00 |
+----+------+-----+--------+-------+---------------------+
2 rows in set (0.00 sec)
mysql> update stu set id=1 where name=qiqi;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from stu;
+----+------+-----+--------+-------+---------------------+
| id | name | age | gender | phone | bir |
+----+------+-----+--------+-------+---------------------+
| 1 | qiqi | 33 | 0 | 153 | 1996-05-06 00:00:00 |
| 12 | wuwu | 25 | 1 | 666 | 2000-06-05 00:00:00 |
+----+------+-----+--------+-------+---------------------+
2 rows in set (0.00 sec)
## 使用update替代delete删除数据
1.给表中，加一个状态列
mysql> alter table stu add status enum(0,1) default 1;
2.使用update删除数据
mysql> update stu set status=0 where name=qiqi;
3.查询的时候，使用where条件查询
ysql> select * from stu where status=1;
+----+------+-----+--------+-------+---------------------+--------+
| id | name | age | gender | phone | bir | status |
+----+------+-----+--------+-------+---------------------+--------+
| 12 | wuwu | 25 | 1 | 666 | 2000-06-05 00:00:00 | 1 |
+----+------+-----+--------+-------+---------------------+--------+
注意：update修改数据库用户的密码，是要flush privileges;修改其他数据，不需要。DCL
Database Control Language
数据 控制 语言
### 赋予权限
5.6和5.7区别：5.7老版本，grant赋予权限，如果该用户不存在，则无法创建，5.6和5.7新版本可以直接创建用户
grant all on *.* to test@% identified by 123;
grant 权限1,权限 on 库.表 to 用户@主机域 identified by 密码;
grant all on *.* to test@% identified by 123 with grant option;
grant all on *.* to zls4@% identified by 123 with max_queries_per_hour 3;
max_queries_per_hour 3 ## 限制该用户一小时内，只能查询3次
grant all on *.* to zls6@% identified by 123
without max_queries_per_hour 3
max_updates_per_hour 1 ## 限制用户一小时，只能执行一次update
max_connections_per_hour 1 ## 限制用户一小时内，只能连接一次数据库
max_user_connections 1 ## 限制用户，只能同时一个用户连接
grant option;
grant all on *.* to zls6@% identified by 123
with max_queries_per_hour 999
max_updates_per_hour 999
max_connections_per_hour 999
max_user_connections 999;
### 回收权限
revoke
revoke 权限 on 库.表 from 用户@主机域;
revoke delete on *.* from dev@%;DQL
Database Query Language
数据 查询 语言
## show
show databases; # 查看数据库
show tables; # 查看表
show tables from zls; # 查看指定数据库下的表，不用切换数据库
show create database 库名; # 查看建库语句
show create table 表名; # 查看建表语句，也是为了查看注释
show create table 库名.表名; # 查看建表语句，也是为了查看注释（不用切换数据库）
show grants for 用户名@主机域; # 查看用户授权语句，也是为了查看该用户的权限
show variables; # 查看所有的内置变量（默认配置）
show variables like %server; # 模糊查询（过滤）
show variables like %server%; # 模糊查询（过滤）
show variables like server%; # 模糊查询（过滤）
show processlist; # 查看后台执行的sql语句
show full processlist; # 查看完整的后台执行的sql语句
show collation; # 查看所有校验规则
show charset; # 查看所有字符集以及该字符集的默认校验规则
## desc
desc 库.表 # 查看表结构
查看执行计划
## explain 查看执行计划 （索引）
## select
[root@db01 ~]# wget http://test.driverzeng.com/MySQL_File/world.sql
mysql> source /root/world.sql
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| linux50 |
| mysql |
| performance_schema |
| test |
| world |
| www |
+--------------------+
mysql> use world
Database changed
mysql> show tables;
+-----------------+
| Tables_in_world |
+-----------------+
| city |
| country |
| countrylanguage |
+-----------------+
3 rows in set (0.00 sec)
## select 常用简单查询
mysql> select * from city; ## 查看该表中所有的字段的记录(所有数据)
mysql> select id,name,countrycode from city; ## 查看指定字段的所有数据
## select 行级查询(翻页功能)
mysql> select id,name,countrycode from city limit 5;
## 翻页功能,从第6开始查到20
mysql> select id,name,countrycode from city limit 5,20;
## select 条件查询
mysql> select * from city where countrycode=CHN;
mysql> select * from city where countrycode=CHN or countrycode=USA;
mysql> select * from city where countrycode=CHN and district=heilongjiang;
### 条件查询结合行级查询
select * from city where countrycode=CHN and district=heilongjiang limit 10;
## select 模糊查询
mysql> select * from city where countrycode like %HN;
mysql> select * from city where countrycode like %HN or countrycode=US%;
## select 排序查询 order by
select * from city where countrycode=CHN order by population; ## 顺序排序
mysql> select * from city where countrycode=CHN order by population desc; ##倒叙排序
## 不加条件,顺序排序
mysql> select * from city order by population;
## 不加条件 倒序排序
mysql> select * from city order by population desc;
## 不重复查询
select distinct 字段名 from 数据表
select distinct Director from movies
## select 范围查询
mysql> select * from city where population > 10000000;
>:大于
<:小于
>=:大于等于
<=:小于等于
<>:不等于
!=:不等于
# in:
mysql> select * from city where countrycode in (CHN,USA);
# or:
mysql> select * from city where countrycode=CHN or countrycode=USA;
# union all 联合查询
mysql> select * from city where countrycode=CHN union all select * from city where countrycode=USA;
## select 分组查询 group by
group by + 聚合函数
聚合函数：
max()：最大值
min()：最小值
sum()：求和
avg()：求平均值`
count()：统计
1.遇到统计想函数
2.形容词前groupby
3.函数中央是名词
4.列名select后添加
# 统计世界上每个国家的总人口数
遇到统计想函数：sum()
形容词前groupby：group by countrycode
函数中央是名词：sum(population)
列名select后添加：国家 人口数 countycode,population
mysql> select countrycode,sum(population) from city group by countrycode;
# 统计中国各个省的人口数量(练习)
遇到统计想函数：sum()
形容词前groupby：group by district
函数中央是名词：sum(population)
名select后添加：省 人口数 district,population
mysql> select district,sum(population) from city where countrycode=CHN group by district;
# 统每个国家的城市数量(练习)
遇到统计想函数：count()
形容词前groupby：group by countrycode
函数中央是名词：count(name)
名select后添加：国家，城市数量 countrycode,count(name)
mysql> select countrycode,count(name) from city group by countrycode;
## 设置别名
select countrycode as 国家,count(name) as 城市数量 from city group by countrycode;select高级用法
传统连接
select tb1.field,tb2.field,tb3.field
from tb1,tb2,tb3
where 等价条件1
and 等价条件2
and 需求条件
注意：两张表，要有等价的条件列
## 多表联查
[zhang3,li4,wang5]
[50,70,80]
t1:student
sid sname
001 zhang3
002 li4
003 wang5
mysql> create table student(
-> sid int(3) zerofill,
-> sname varchar(10)
-> );
insert into student(sid,sname) value(1,zhang3),(2,li4),(3,wang5);
mysql> select * from student;
+------+--------+
| sid | sname |
+------+--------+
| 001 | zhang3 |
| 002 | li4 |
| 003 | wang5 |
+------+--------+
t2:score
sid smark
001 50
002 70
003 80
mysql> create table score(
-> sid int(3) zerofill,
-> smark float(3,1)
-> );
mysql> insert into score value(1,50),(2,70),(3,80);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| score |
| student |
| wsh |
+----------------+
3 rows in set (0.00 sec)
## 查询出wang5的成绩
### 传统连接
mysql> select student.sname,score.smark from student,score where student.sid=score.sid and student.sname=wang5;
+-------+-------+
| sname | smark |
+-------+-------+
| wang5 | 80.0 |
+-------+-------+
# 连表查询的前提：两张表，必须有关联的字段
## 世界上小于100人的人口城市是哪个国家的？
mysql> use world;
mysql> select country.name as 国家,city.name as 城市,city.population as 城市人口 from city,country where city.countrycode=country.code and city.population < 100;
+----------+-----------+--------------+
| 国家 | 城市 | 城市人口 |
+----------+-----------+--------------+
| Pitcairn | Adamstown | 42 |
+----------+-----------+--------------+
1 row in set (0.02 sec)
## 世界上大于10000000人口数量的城市在哪个国家，说什么语言？
国家名 城市名 城市人口数量 语言
mysql> select country.name,city.name,city.population,countrylanguage.language
-> from country,city,countrylanguage
-> where country.code=city.countrycode
-> and country.code=countrylanguage.countrycode
-> and city.population > 10000000;
+-------+-----------------+------------+-----------+
| name | name | population | language |
+-------+-----------------+------------+-----------+
| India | Mumbai (Bombay) | 10500000 | Asami |
| India | Mumbai (Bombay) | 10500000 | Bengali |
| India | Mumbai (Bombay) | 10500000 | Gujarati |
| India | Mumbai (Bombay) | 10500000 | Hindi |
| India | Mumbai (Bombay) | 10500000 | Kannada |
| India | Mumbai (Bombay) | 10500000 | Malajalam |
| India | Mumbai (Bombay) | 10500000 | Marathi |
| India | Mumbai (Bombay) | 10500000 | Orija |
| India | Mumbai (Bombay) | 10500000 | Punjabi |
| India | Mumbai (Bombay) | 10500000 | Tamil |
| India | Mumbai (Bombay) | 10500000 | Telugu |
| India | Mumbai (Bombay) | 10500000 | Urdu |
+-------+-----------------+------------+-----------+
12 rows in set (0.03 sec)
自连接（NATURAL JOIN）
natural join
select tb1.field1,tb2.field,tb1.field2
from tb1 natural join tb2
where 需求条件
注意：两张表，要有等价的条件列，并且列名（字段名）也要一样
city 国家代码：countrycode
country 国家代码： code
countrylanguage 国家代码： countrycode
## 说english的城市有哪些，他们的国家代码是什么？
select city.countrycode,city.name,countrylanguage.language
from city natural join countrylanguage
where countrylanguage.language=english;
## 每个国家有几个城市说英语，他们的国家代码是什么？
select city.countrycode as 国家代码,count(city.name) as 城市数量,countrylanguage.language as 语言
from city natural join countrylanguage
where countrylanguage.language=english
group by countrycode;
## 每个国家有几个城市说英语，他们的国家代码是什么？ 按城市数量排序
select city.countrycode as 国家代码,count(city.name) as 城市数量,countrylanguage.language as 语言
from city natural join countrylanguage
where countrylanguage.language=english
group by countrycode order by 城市数量;内连接（join on）
## 两表
select tb1.field1,tb2.field,tb1.field2
from tb1 join tb2
on 等价条件
where 需求条件
### 多表
select tb1.field,tb2.field,tb3.field
from tb1
join tb2
on 等价条件1
join tb3
on 等价条件2
where 需求条件
注意：两张表，要有等价的条件列，大表在前，小表在后
## 每个国家有几个城市说英语，他们的国家代码是什么？
select city.countrycode as 国家代码,count(city.name) as 城市数量,countrylanguage.language as 语言
from city join countrylanguage
on city.countrycode=countrylanguage.countrycode
where countrylanguage.language=english
group by city.countrycode;
## 世界上大于10000000人口数量的城市在哪个国家，说什么语言？
1 jion 2 on A
表1 jion 表2 on 等价条件A join 表3 on 等价条件B
**** 传统连接 ****
select country.name,city.name,city.population,countrylanguage.language
from country,city,countrylanguage
where country.code=city.countrycode
and country.code=countrylanguage.countrycode
and city.population > 10000000;
**** 内连接 三表连查 ****
select country.name,city.name,city.population,countrylanguage.language
from country
join city
on country.code=city.countrycode
join countrylanguage
on country.code=countrylanguage.countrycode
where city.population > 10000000;
外连接(了解即可)
## 左外连接 left join
- 左外连接
left join
select tb1.field1,tb2.field,tb1.field2
from tb1 left join tb2
on 等价条件
and 需求条件
显示左边表的内容，tb1，右边表结果显示NULL
- 右外连接
right join
select tb1.field1,tb2.field,tb1.field2
from tb1 right join tb2
on 等价条件
显示右边表的内容，tb2，左边表结果显示NULL
select city.name,city.countrycode,country.name from city left join country on city.countrycode=country.code and city.population<100;
## 右外连接 right join
select city.name,city.countrycode,country.name from city right join country on city.countrycode=country.code and city.population<100;联合查询
#范围查询OR语句
mysql> select * from city where countrycode=CHN or countrycode=USA;
#范围查询IN语句
mysql> select * from city where countrycode in (CHN,USA);
# 替换为：
mysql> select * from city where countrycode=CHN union all select * from city where countrycode=USA;
union：去重复合并
union all ：不去重复
使用情况：union < union all字符集设置
操作系统设置字符集
## CentOS6
[root@db01 ~]# source /etc/sysconfig/i18n
[root@db01 ~]# echo $LANG
zh_CN.UTF-8
## CentOS7
[root@db01 ~]# echo $LANG
en_US.UTF-8
# 如不是utf8
[root@db01 ~]# vim /etc/locale.conf
LANG="en_US.UTF-8"连接工具设置字符集
Xshell
## windows
GB2312 国标
GBK 国标扩建库建表级别设置字符集
## 建库设置字符集
mysql> create databae wsh charset utf8 collate utf8_general_ci;
## 建表设置字符集
create table test(
id int,
name varchar(10)
) default charset utf8;数据库配置设置字符集
## 一般只有在二进制安装的mysql的时候默认为非utf8
[root@db02 ~]# vim /etc/my.cnf
[mysqld]
character_set_server=utf8练习题
建库
库名：linux50 字符集：utf8 校验规则：utf8_general_ci
mysql> create database linux50 charset utf8 collate utf8_general_ci;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| linux50 |
| mysql |
| performance_schema |
| test |
+--------------------+
5 rows in set (0.11 sec)建表
表一
表名：student（学生表）
字段 数据类型要求 是否为空 注释
sno 最多20位 否 学号（主键）
sname 可变长 否 学生姓名
sage 最小整数，非负数 否 学生年龄
ssex 0，1 否 学生性别（1是男，0是女s）默认为男）
sbirthday 时间类型 默认为空 学生生日
class 可变长 否 学生班级
mysql> use linux50;
Database changed
mysql> create table student(
-> sno bigint(20) primary key auto_increment comment 学号(主键),
-> sname varchar(10) not null comment 学生姓名,
-> sage tinyint unsigned not null comment 学生年龄,
-> ssex enum(0,1) not null default 1 comment 学生性别（1是男，0是女s）默认为 男）,
-> sbirthday datetime default null comment 学生生日,
-> class varchar(5) not null comment 学生班级
-> );
Query OK, 0 rows affected (0.01 sec)
mysql> desc student;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| sno | bigint(20) | NO | PRI | NULL | auto_increment |
| sname | varchar(10) | NO | | NULL | |
| sage | tinyint(3) unsigned | NO | | NULL | |
| ssex | enum(0,1) | NO | | 1 | |
| sbirthday | datetime | YES | | NULL | |
| class | varchar(5) | NO | | NULL | |
+-----------+---------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
表二
表名：course（课程表）
字段 数据类型要求 是否为空 注释
cno 最多20位 否 课程号（主键）
cname 可变长 否 课程名称
tno 可变长 否 教师编号
mysql> create table course(
-> cno bigint(20) primary key auto_increment comment 课程号(主键),
-> cname varchar(10) not null comment 课程名称,
-> tno varchar(3) not null comment 教师编号
-> );
Query OK, 0 rows affected (0.01 sec)
mysql> desc course;
+-------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+----------------+
| cno | bigint(20) | NO | PRI | NULL | auto_increment |
| cname | varchar(10) | NO | | NULL | |
| tno | varchar(3) | NO | | NULL | |
+-------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)表三
表名：score（成绩表）
字段 数据类型要求 是否为空 注释
sno 最多20位 否 学号（主键）
cno 最多20位 否 课程号（主键）
mark 浮点数(4,1) 否 成绩
mysql> create table score(
-> sno bigint(20) not null comment 学号（主键）,
-> cno bigint(20) not null comment 课程号（主键）,
-> mark float(4,1) not null comment 成绩
-> );
Query OK, 0 rows affected (0.01 sec)
mysql> desc score;
+-------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| sno | bigint(20) | NO | | NULL | |
| cno | bigint(20) | NO | | NULL | |
| mark | float(4,1) | NO | | NULL | |
+-------+------------+------+-----+---------+-------+
3 rows in set (0.00 sec)表四
表名：teacher（教师表）
字段 数据类型要求 是否为空 注释
tno 最多20位 否 教师编号（主键）
tname 可变长 否 教师姓名
tage 最小整数，非负数 否 教师年龄
tsex 0，1 否 教师性别（1是男，0是女）默认为男）
prof 可变长 是 教师职称
depart 可变长 否 教师部门
mysql> create table teacher(
-> tno bigint(3) zerofill primary key auto_increment comment 教师编号（主键）,
-> tname varchar(10) not null comment 教师编号（主键）,
-> tage tinyint unsigned not null comment 教师年龄,
-> tsex enum(0,1) not null comment 教师性别（1是男，0是女）默认为男）,
-> prof varchar(10) null comment 教师职称,
-> depart varchar(10) not null comment 教师部门
-> );
Query OK, 0 rows affected (0.01 sec)
mysql> desc teacher;
+--------+-----------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+-----------------------------+------+-----+---------+----------------+
| tno | bigint(3) unsigned zerofill | NO | PRI | NULL | auto_increment |
| tname | varchar(10) | NO | | NULL | |
| tage | tinyint(3) unsigned | NO | | NULL | |
| tsex | enum(0,1) | NO | | NULL | |
| prof | varchar(10) | YES | | NULL | |
| depart | varchar(10) | NO | | NULL | |
+--------+-----------------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
## zerofill 零填充插入数据练习
1.将自己班级小组所有人员信息插入到student表中（数据自定义）
mysql> insert into student(sname,sage,ssex,sbirthday,class) value
-> (徐导,20,1,now(),1),
-> (曾导,18,1,now(),1),
-> (李导,25,1,now(),2);
Query OK, 3 rows affected (0.01 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select * from student;
+-----+--------+------+------+---------------------+-------+
| sno | sname | sage | ssex | sbirthday | class |
+-----+--------+------+------+---------------------+-------+
| 1 | 徐导 | 20 | 1 | 2022-08-14 16:22:39 | 1 |
| 2 | 曾导 | 18 | 1 | 2022-08-14 16:22:39 | 1 |
| 3 | 李导 | 25 | 1 | 2022-08-14 16:22:39 | 2 |
+-----+--------+------+------+---------------------+-------+
3 rows in set (0.00 sec)2.将曾志高翔、徐亮伟、李永义信息插入教师表中（数据自定义）
mysql> insert into teacher(tname,tage,tsex,prof,depart)
-> value(曾志高翔,18,1,教学总监,语言系),
-> (徐亮伟,50,1,讲师,文学系),
-> (李永义,80,1,助教,科学系);
Query OK, 3 rows affected (0.01 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select * from teacher;
+-----+--------------+------+------+--------------+-----------+
| tno | tname | tage | tsex | prof | depart |
+-----+--------------+------+------+--------------+-----------+
| 001 | 曾志高翔 | 18 | 1 | 教学总监 | 语言系 |
| 002 | 徐亮伟 | 50 | 1 | 讲师 | 文学系 |
| 003 | 李永义 | 80 | 1 | 助教 | 科学系 |
+-----+--------------+------+------+--------------+-----------+
3 rows in set (0.00 sec)3.将数学、语文、英语学科插入到课程表中（数据自定义）
mysql> insert into course(cno,cname,tno) value(1,英语,001),(2,语文,002),(3,数学,003);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select * from course;
+-----+--------+-----+
| cno | cname | tno |
+-----+--------+-----+
| 1 | 英语 | 001 |
| 2 | 语文 | 002 |
| 3 | 数学 | 003 |
+-----+--------+-----+
3 rows in set (0.00 sec)4.将分数插入到成绩表中（数据自定义）
mysql> insert into score(sno,cno,mark) value(1,1,90.0),
-> (2,1,10.0),
-> (3,1,60.0),
-> (1,2,90.0),
-> (2,2,99.5),
-> (3,2,80.0),
-> (1,3,80.5),
-> (2,3,60.0),
-> (3,3,88.0);
Query OK, 9 rows affected (0.00 sec)
Records: 9 Duplicates: 0 Warnings: 0
mysql> select * from score;
+-----+-----+------+
| sno | cno | mark |
+-----+-----+------+
| 1 | 1 | 90.0 |
| 2 | 1 | 10.0 |
| 3 | 1 | 60.0 |
| 1 | 2 | 90.0 |
| 2 | 2 | 99.5 |
| 3 | 2 | 80.0 |
| 1 | 3 | 80.5 |
| 2 | 3 | 60.0 |
| 3 | 3 | 88.0 |
+-----+-----+------+
9 rows in set (0.00 sec)查询练习
1.查询student表中的所有记录的sname、ssex和class列。
mysql> select sname,ssex,class from student;
+--------+------+-------+
| sname | ssex | class |
+--------+------+-------+
| 徐导 | 1 | 1 |
| 曾导 | 1 | 1 |
| 李导 | 1 | 2 |
+--------+------+-------+
3 rows in set (0.01 sec)2.查询教师所有的单位即不重复的depart列。
mysql> insert into teacher(tname,tage,tsex,prof,depart)
-> value(曾志高翔,18,1,教学总监,语言系),
-> (徐亮伟,50,1,讲师,文学系),
-> (李永义,80,1,助教,科学系);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select * from teacher;
+-----+--------------+------+------+--------------+-----------+
| tno | tname | tage | tsex | prof | depart |
+-----+--------------+------+------+--------------+-----------+
| 001 | 曾志高翔 | 18 | 1 | 教学总监 | 语言系 |
| 002 | 徐亮伟 | 50 | 1 | 讲师 | 文学系 |
| 003 | 李永义 | 80 | 1 | 助教 | 科学系 |
| 004 | 曾志高翔 | 18 | 1 | 教学总监 | 语言系 |
| 005 | 徐亮伟 | 50 | 1 | 讲师 | 文学系 |
| 006 | 李永义 | 80 | 1 | 助教 | 科学系 |
+-----+--------------+------+------+--------------+-----------+
6 rows in set (0.00 sec)
mysql> select distinct(depart) from teacher;
+-----------+
| depart |
+-----------+
| 语言系 |
| 文学系 |
| 科学系 |
+-----------+
3 rows in set (0.00 sec)3.查询student表的所有记录。
mysql> select * from student;
+-----+--------+------+------+---------------------+-------+
| sno | sname | sage | ssex | sbirthday | class |
+-----+--------+------+------+---------------------+-------+
| 1 | 徐导 | 20 | 1 | 2022-08-14 16:22:39 | 1 |
| 2 | 曾导 | 18 | 1 | 2022-08-14 16:22:39 | 1 |
| 3 | 李导 | 25 | 1 | 2022-08-14 16:22:39 | 2 |
+-----+--------+------+------+---------------------+-------+
3 rows in set (0.00 sec)4.查询score表中成绩在60到80之间的所有记录。
mysql> select * from score where mark>=60 and mark<=80;
+-----+-----+------+
| sno | cno | mark |
+-----+-----+------+
| 3 | 1 | 60.0 |
| 3 | 2 | 80.0 |
| 2 | 3 | 60.0 |
+-----+-----+------+
3 rows in set (0.00 sec)5.查询score表中成绩为85，86或88的记录。
mysql> select * from score where mark in (85,86,88);
+-----+-----+------+
| sno | cno | mark |
+-----+-----+------+
| 3 | 3 | 88.0 |
+-----+-----+------+
1 row in set (0.00 sec)6.查询student表中4班或性别为“女”的同学记录。
mysql> select * from student where class=1 or ssex=0;
+-----+--------+------+------+---------------------+-------+
| sno | sname | sage | ssex | sbirthday | class |
+-----+--------+------+------+---------------------+-------+
| 1 | 徐导 | 20 | 1 | 2022-08-14 16:22:39 | 1 |
| 2 | 曾导 | 18 | 1 | 2022-08-14 16:22:39 | 1 |
+-----+--------+------+------+---------------------+-------+
2 rows in set (0.00 sec)7.以class降序查询Student表的所有记录。
mysql> select * from student order by class desc;
+-----+--------+------+------+---------------------+-------+
| sno | sname | sage | ssex | sbirthday | class |
+-----+--------+------+------+---------------------+-------+
| 3 | 李导 | 25 | 1 | 2022-08-14 16:22:39 | 2 |
| 1 | 徐导 | 20 | 1 | 2022-08-14 16:22:39 | 1 |
| 2 | 曾导 | 18 | 1 | 2022-08-14 16:22:39 | 1 |
+-----+--------+------+------+---------------------+-------+
3 rows in set (0.00 sec)8.以cno升序、mark降序查询Score表的所有记录
mysql> select * from score order by cno , mark desc;
+-----+-----+------+
| sno | cno | mark |
+-----+-----+------+
| 1 | 1 | 90.0 |
| 3 | 1 | 60.0 |
| 2 | 1 | 10.0 |
| 2 | 2 | 99.5 |
| 1 | 2 | 90.0 |
| 3 | 2 | 80.0 |
| 3 | 3 | 88.0 |
| 1 | 3 | 80.5 |
| 2 | 3 | 60.0 |
+-----+-----+------+
9 rows in set (0.00 sec)9.查询4班的学生人数。
mysql> select count(class) from student where class=2 group by class;
+--------------+
| count(class) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)10.查询”曾导“教师任课的学生成绩。
## 传统连接
mysql> select teacher.tname,course.cname,student.sname,score.mark
-> from teacher,course,student,score
-> where teacher.tno=course.tno
-> and course.cno=score.cno
-> and student.sno=score.sno
-> and teacher.tname=曾志高翔;
## 内连接
mysql> select teacher.tname,course.cname,student.sname,score.mark
-> from teacher join course
-> on teacher.tno=course.tno
-> join score
-> on course.cno=score.cno
-> join student
-> on student.sno=score.sno
-> where teacher.tname=曾志高翔;
+--------------+--------+--------+------+
| tname | cname | sname | mark |
+--------------+--------+--------+------+
| 曾志高翔 | 英语 | 徐导 | 90.0 |
| 曾志高翔 | 英语 | 曾导 | 10.0 |
| 曾志高翔 | 英语 | 李导 | 60.0 |
+--------------+--------+--------+------+
3 rows in set (0.00 sec)11.查询语文课程所有男生的成绩并且查出对应课程的教师名，职称，及所在部门。
## 传统连接
mysql> select teacher.tname,teacher.prof,teacher.depart,student.sname,course.cname,score.mark
-> from teacher,course,student,score
-> where teacher.tno=course.tno
-> and course.cno=score.cno
-> and student.sno=score.sno
-> and student.ssex=1
-> and course.cname=语文;
## 内连接
mysql> select teacher.tname,teacher.prof,teacher.depart,student.sname,course.cname,score.mark
-> from teacher join course
-> on teacher.tno=course.tno
-> join score
-> on course.cno=score.cno
-> join student
-> on student.sno=score.sno
-> where student.ssex=1
-> and course.cname=语文;
+-----------+--------+-----------+--------+--------+------+
| tname | prof | depart | sname | cname | mark |
+-----------+--------+-----------+--------+--------+------+
| 徐亮伟 | 讲师 | 文学系 | 徐导 | 语文 | 90.0 |
| 徐亮伟 | 讲师 | 文学系 | 曾导 | 语文 | 99.5 |
| 徐亮伟 | 讲师 | 文学系 | 李导 | 语文 | 80.0 |
+-----------+--------+-----------+--------+--------+------+
3 rows in set (0.00 sec)12.把11题查出的成绩按照降序排序。
mysql> select teacher.tname,teacher.prof,teacher.depart,student.sname,course.cname,score.mark
-> from teacher join course
-> on teacher.tno=course.tno
-> join score
-> on course.cno=score.cno
-> join student
-> on student.sno=score.sno
-> where student.ssex=1
-> and course.cname=语文
-> order by score.mark desc;
+-----------+--------+-----------+--------+--------+------+
| tname | prof | depart | sname | cname | mark |
+-----------+--------+-----------+--------+--------+------+
| 徐亮伟 | 讲师 | 文学系 | 曾导 | 语文 | 99.5 |
| 徐亮伟 | 讲师 | 文学系 | 徐导 | 语文 | 90.0 |
| 徐亮伟 | 讲师 | 文学系 | 李导 | 语文 | 80.0 |
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