mysql的程序组成
目录
mysql的程序组成
- 客户端
- mysql：CLI交互式客户端程序
- mysql_secure_installation：安全初始化，强烈建议安装完以后执行此命令
- mysqldump：mysql备份工具
- mysqladmin
- 服务器端
- mysqld
[root@localhost ~]# mysql
mysql mysqld-debug mysql_secure_installation
mysqladmin mysqld_pre_systemd mysqlshow
mysqlbinlog mysqldump mysqlslap
mysqlcheck mysqldumpslow mysql_ssl_rsa_setup
mysql_config mysqlimport mysql_tzinfo_to_sql
mysql_config-64 mysql_install_db mysql_upgrade
mysql_config_editor mysql_plugin
mysqld mysqlpump
mysql工具使用
语法：mysql [OPTIONS] [database]
常用的OPTIONS：
-uUSERNAME //指定用户名，默认为root
-hHOST //指定服务器主机，默认为localhost，推荐使用ip地址
-pPASSWORD //指定用户的密码
-P# //指定数据库监听的端口，这里的#需用实际的端口号代替，如-P3307
-V //查看当前使用的mysql版本
-e //不登录mysql执行sql语句后退出，常用于脚本
指定用户名，指定用户的密码
[root@localhost ~]# mysql -uroot -pLuojialong123!
不登录 mysql 执行 sql 语句后退出，常用于脚本
[root@localhost ~]# mysql -uroot -pLuojialong123! -e 'show databases'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
[root@localhost ~]#
服务器监听的两种 socket 地址
| socket类型 | 说明 |
|---|---|
| ip socket | 默认监听在tcp的3306端口，支持远程通信 |
| unix sock | 监听在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock)仅支持本地通信server地址只能是：localhost，127.0.0.1 |
mysql数据库操作
数值：
| 数值类型 | 大小（bytes） | 范围（有符号） | 范围（无符号） | 用途 |
|---|---|---|---|---|
| tinyint | 1 | (-128,127) | (0,255) | 小整数值 |
| smallint | 2 | (-32768,32767) | (0,65535) | 大整数值 |
| mediumint | 3 | (-8388608,8388607) | (0,16777215) | 大整数值 |
| int 或 integer | 4 | (-2147483648,2147483647) | (0,4294967295) | 大整数值 |
| bigint | 8 | (-9,223,372,036,854,775,808，9 223 372 036 854 775 807) | (0，18 446 744 073 709 551 615) | 极大整数值 |
| float | 4 | (-3.402 823 466 E+38，-1.175 494 351 E-38)，0，(1.175 494 351 E-38，3.402 823 466 351 E+38)) | 0，(1.175 494 351 E-38，3.402 823 466 E+38) | 单精度，浮点数值 |
| double | 8 | (-1.797 693 134 862 315 7 E+308，-2.225 073 858 507 201 4 E-308)，0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308) | 0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308) | 双精度，浮点数值 |
| decimal | 对 decimal(M,D) ，如果 M>D ，为 M+2 否则为 D+2 | 依赖于 M 和 D 的值 | 依赖于 M 和 D 的值 | 小数值 |
日期和时间：
| 数值类型 | 大小（bytes） | 范围 | 格式 | 用途 |
|---|---|---|---|---|
| date | 3 | 1000-01-01/9999-12-31 | YYYY-MM-DD | 日期值 |
| time | 3 | ‘-838:59:59’/‘838:59:59’ | HH:MM:SS | 时间值或持续时间 |
| year | 1 | 1901/2155 | YYYY | 年份值 |
| datetime | 8 | 1000-01-01 00:00:00/9999-12-31 23:59:59 | YYYY-MM-DD HH:MM:SS | 混合日期和时间值 |
| timestamp | 4 | 1970-01-01 00:00:00/2038结束时间是第 2147483647 秒，北京时间 2038-1-19 11:14:07，格林尼治时间 2038年1月19日 凌晨 03:14:07 | YYYYMMDDHHMMSS | 混合日期和时间值，时间戳 |
字符串：
| 数值类型 | 大小（bytes） | 用途 |
|---|---|---|
| char | 0~255 | 定长字符串 |
| varchar | 0~65535 | 变长字符串 |
| tinyblob | 0~255 | 不超过 255 个字符的二进制字符串 |
| tinytext | 0~255 | 短文本字符串 |
| blob | 0~65535 | 二进制形式的长文本数据 |
| text | 0~65535 | 长文本数据 |
| mediumblob | 0~16777215 | 二进制形式的中等长度文本数据 |
| mediumtext | 0~16777215 | 中等长度文本数据 |
| longblob | 0~4294967295 | 二进制形式的极大文本数据 |
| longtext | 0~4294967295 | 极大文本数据 |
DDL操作
数据库操作
- create database [if not exists] DB_NAME; ：创建数据库
- show databases; ：查看当前实例有哪些数据库
- use DATABASES; ：进入数据库
- drop database [if exists] DB_NAME; ：删除数据库
表操作
- create table TABLE_NAME (COL1 DATATYPE 修饰符,COL2 DATATYPE 修饰符) engine=‘存储引擎类型’; ：创建表
- show tables; ：查看当前数据库有哪些表
- desc [DB_NAME.] TABLE_NAME; ：查看表的结构信息
- drop table [if exists] TABLE_NAME; ：删除表
用户操作
表操作
mysql 用户帐号由两部分组成，如 ‘USERNAME’@‘HOST’ ，表示此 USERNAME 只能从此 HOST 上远程登录
这里（‘USERNAME’@‘HOST’）的 HOST 用于限制此用户可通过哪些主机远程连接 mysql 程序，其值可为：
-
IP 地址，如：172.16.12.129
-
通配符
-
%：匹配任意长度的任意字符，常用于设置允许从任何主机登录
-
_：匹配任意单个字符
-
create user ‘USERNAME’@‘主机’ [identified by ‘PASSWORD’];：数据库用户创建
mysql> create database ljl;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| ljl |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
- drop user ‘USERNAME’@‘主机’; ：删除数据库用户
mysql> drop database ljl;
Query OK, 0 rows affected (0.35 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
用户操作
mysql用户帐号由两部分组成，如'USERNAME'@'HOST'，表示此USERNAME只能从此HOST上远程登录
这里（'USERNAME'@'HOST'）的HOST用于限制此用户可通过哪些主机远程连接mysql程序，其值可为：
- IP地址，如：172.16.12.129
- 通配符
- %：匹配任意长度的任意字符，常用于设置允许从任何主机登录
- _：匹配任意单个字符
数据库用户创建
mysql> create user 'tom'@'localhost' identified by 'Luojialong123!';
Query OK, 0 rows affected (0.00 sec)
删除数据库用户
mysql> drop user 'tom'@'localhost';
Query OK, 0 rows affected (0.00 sec)
查看命令SHOW
查看支持的所有字符集
mysql> show character set;
+----------+---------------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
| gb18030 | China National Standard GB18030 | gb18030_chinese_ci | 4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)
查看当前数据库支持的所有存储引擎
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
查看数据库信息
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| ljl |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
不进入某数据库而列出其包含的所有表
mysql> show tables from ljl;
+---------------+
| Tables_in_ljl |
+---------------+
| wangqing |
+---------------+
1 row in set (0.00 sec)
查看表结构
mysql> desc ljl.wangqing;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.43 sec)
查看某表的创建命令
mysql> show create table ljl.wangqing;
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
| wangqing | CREATE TABLE `wangqing` (
`id` int(11) NOT NULL,
`name` varchar(100) NOT NULL,
`age` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
查看某表的状态
mysql> show table status like 'wangqing'\G
*************************** 1. row ***************************
Name: wangqing
Engine: InnoDB
Version: 10
Row_format: Dynamic
Rows: 0
Avg_row_length: 0
Data_length: 16384
Max_data_length: 0
Index_length: 0
Data_free: 0
Auto_increment: NULL
Create_time: 2022-07-25 21:06:00
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
DML操作
INSERT语句
DML操作之增操作insert
mysql> use ljl
Database changed
mysql> insert into wangqing(id,name,age) values(1,'zhangsan',22),(2,'lisi',23);
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
SELECT语句
字段column表示法
| 表示符 | 代表什么？ |
|---|---|
| * | 所有字段 |
| as | 字段别名，如col1 AS alias1当表名很长时用别名代替 |
条件判断语句WHERE
| 操作类型 | 常用操作符 |
|---|---|
| 操作符 | >，<，>=，<=，=，!= BETWEEN column# AND column# ;LIKE：模糊匹配 ;RLIKE：基于正则表达式进行模式匹配 ;IS NOT NULL：非空 ;IS NULL：空 |
| 条件逻辑操作 | AND OR NOT |
ORDER BY：排序，默认为升序（ASC）
| ORDER BY语句 | 意义 |
|---|---|
| ORDER BY ‘column_name' | 根据column_name进行升序排序 |
| ORDER BY 'column_name' DESC | 根据column_name进行降序排序 |
| ORDER BY ’column_name' LIMIT 2 | 根据column_name进行升序排序并只取前2个结果 |
| ORDER BY ‘column_name' LIMIT 1,2 | 根据column_name进行升序排序并且略过第1个结果取后面的2个结果 |
DML操作之查操作select
mysql> select * from wangqing;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
| 2 | lisi | 23 |
+----+----------+------+
2 rows in set (0.00 sec)
mysql> select name from wangqing;
+----------+
| name |
+----------+
| zhangsan |
| lisi |
+----------+
2 rows in set (0.00 sec)
mysql> select * from wangqing where age>22;
+----+------+------+
| id | name | age |
+----+------+------+
| 2 | lisi | 23 |
+----+------+------+
1 row in set (0.00 sec)
mysql> select * from wangqing where age>=22;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
| 2 | lisi | 23 |
+----+----------+------+
2 rows in set (0.00 sec)
mysql> select * from wangqing where age<23;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
+----+----------+------+
1 row in set (0.00 sec)
mysql> select * from wangqing where age<=23;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
| 2 | lisi | 23 |
+----+----------+------+
2 rows in set (0.00 sec)
mysql> select * from wangqing where age=23;
+----+------+------+
| id | name | age |
+----+------+------+
| 2 | lisi | 23 |
+----+------+------+
1 row in set (0.00 sec)
mysql> select * from wangqing where age!=23;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
+----+----------+------+
1 row in set (0.00 sec)
ORDER BY：排序，默认为升序（ASC）
mysql> select * from wangqing order by age;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
| 2 | lisi | 23 |
+----+----------+------+
2 rows in set (0.00 sec)
mysql> select * from wangqing order by age desc;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 2 | lisi | 23 |
| 1 | zhangsan | 22 |
+----+----------+------+
2 rows in set (0.00 sec)
update语句
DML操作之改操作update
mysql> update wangqing set age = 24 where name = 'lisi';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
delete语句
DML操作之删操作delete
mysql> select * from wangqing;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
| 2 | lisi | 24 |
+----+----------+------+
2 rows in set (0.00 sec)
mysql> delete from wangqing where age = 24;
Query OK, 1 row affected (0.01 sec)
mysql> select * from wangqing;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | zhangsan | 22 |
+----+----------+------+
1 row in set (0.00 sec)
mysql> delete from wangqing;
Query OK, 1 row affected (0.00 sec)
mysql> select * from wangqing;
Empty set (0.00 sec)
mysql> desc wangqing;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
truncate语句
truncate与delete的区别：
| 语句类型 | 特点 |
|---|---|
| delete | DELETE删除表内容时仅删除内容，但会保留表结构.DELETE语句每次删除一行，并在事务日志中为所删除的每行记录一项.可以通过回滚事务日志恢复数据.非常占用空间 |
| truncate | 删除表中所有数据，且无法恢复.表结构、约束和索引等保持不变，新添加的行计数值重置为初始值.执行速度比DELETE快，且使用的系统和事务日志资源少.通过释放存储表数据所用的数据页来删除数据，并且只在事务日志中记录页的释放.对于有外键约束引用的表，不能使用TRUNCATE TABLE删除数据.不能用于加入了索引视图的表 |
DCL操作
创建授权grant
权限类型(priv_type)
| 权限类型 | 代表什么？ |
|---|---|
| ALL | 所有权限 |
| SELECT | 读取内容的权限 |
| INSERT | 插入内容的权限 |
| UPDATE | 更新内容的权限 |
| DELETE | 删除内容的权限 |
指定要操作的对象db_name.table_name
| 表示方式 | 意义 |
|---|---|
| ` * .* | 所有库的所有表 |
| db_name | 指定库的所有表 |
| db_name.table_name | 指定库的指定表 |
mysql> grant all on *.* to '%'@'%' identified by 'Luojialong123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)
查看授权
mysql> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
查看指定用户localhost的授权信息
mysql> show grants for 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
取消授权REVOKE
//语法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';
mysql> REVOKE ALL ON *.* FROM 'wangqing'@'172.16.12.129';
Query OK, 0 rows affected (0.00 sec)
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)
注意：mysql服务进程启动时会读取mysql库中的所有授权表至内存中：
- GRANT或REVOKE等执行权限操作会保存于表中，mysql的服务进程会自动重读授权表，并更新至内存中
- 对于不能够或不能及时重读授权表的命令，可手动让mysql的服务进程重读授权表
实战案例
1.搭建mysql服务
2.创建一个以你名字为名的数据库，并创建一张表student，该表包含三个字段（id，name，age），表结构如下：
mysql> create table student (id int not null, name VARCHAR(100) NOT NULL,age tinyint);
Query OK, 0 rows affected (0.42 sec)
mysql> desc student;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
3.查看下该新建的表有无内容（用select语句）
mysql> select * from student;
Empty set (0.00 sec)
4.往新建的student表中插入数据（用insert语句），结果应如下所示：
mysql> insert into student (id,name,age) values(1,'tom',20),(2,'jerry',23),(3,'wangqing',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',null),(8,'chenshuo',10),(9,'wangwu',3),(10,'qiuyi',15),(11,'qiuxiaotian',20);
Query OK, 11 rows affected (0.01 sec)
Records: 11 Duplicates: 0 Warnings: 0
mysql> select * from student;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | NULL |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
11 rows in set (0.00 sec)
5.修改lisi的年龄为50
mysql> update student set age=50 where name= 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from student;
| 7 | lisi | 50 |
6.以age字段降序排序
mysql> select * from student order by age desc;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 7 | lisi | 50 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 3 | wangqing | 25 |
| 2 | jerry | 23 |
| 1 | tom | 20 |
| 6 | zhangshan | 20 |
| 11 | qiuxiaotian | 20 |
| 10 | qiuyi | 15 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
+----+-------------+------+
11 rows in set (0.00 sec)
7.查询student表中年龄最小的3位同学跳过前2位
mysql> select * from student order by age limit 2,3;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 10 | qiuyi | 15 |
| 1 | tom | 20 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
3 rows in set (0.01 sec)
8.查询student表中年龄最大的4位同学
mysql> select * from student order by age desc limit 4;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 7 | lisi | 50 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 3 | wangqing | 25 |
+----+-----------+------+
4 rows in set (0.00 sec)
9.查询student表中名字叫zhangshan的记录
mysql> select * from student where name='zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
+----+-----------+------+
2 rows in set (0.00 sec)
10.查询student表中名字叫zhangshan且年龄大于20岁的记录
mysql> select * from student where name='zhangshan' and age >= 20;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
+----+-----------+------+
2 rows in set (0.00 sec)
11.查询student表中年龄在23到30之间的记录
mysql> select * from student where age between 23 and 30;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
+----+-----------+------+
4 rows in set (0.09 sec)
12.修改wangwu的年龄为100
mysql> update student set age=100 where name='wangwu';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from student where name='wangwu';
+----+--------+------+
| id | name | age |
+----+--------+------+
| 9 | wangwu | 100 |
+----+--------+------+
1 row in set (0.00 sec)
13.删除student中名字叫zhangshan且年龄小于等于20的记录
mysql> delete from student where name='zhangshan' and age<=20;
Query OK, 1 row affected (0.01 sec)
mysql> select * from student where name='zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
+----+-----------+------+
1 row in set (0.00 sec)
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