1.MySQL存储引擎的配置
查看服务支持的存储引擎
查看默认存储类型
更改表的存储引擎
设置数据库服务默认使用的存储引擎
1.1 查看存储引擎信息
mysql> SHOW ENGINESG
1.2 查看默认存储类型
mysql> SHOW VARIABLES LIKE 'default_storage_engine';
+------------------------+--------+
| Variable_name | Value |
+------------------------+--------+
| default_storage_engine | InnoDB |
+------------------------+--------+
1.3 修改默认存储引擎
1.3.1 指令修改
mysql> SET default_storage_engine=MyISAM;
mysql> SHOW VARIABLES LIKE 'default_storage_engine';
+------------------------+--------+
| Variable_name | Value |
+------------------------+--------+
| default_storage_engine | MyISAM |
+------------------------+--------+
1.3.2 配置文件修改
]# vim /etc/my.cnf
...
default_storage_engine=MEMORY //改用MEMORY引擎
]# systemctl restart mysqld.service
mysql> SHOW VARIABLES LIKE 'default_storage_engine';
2.数据导入、导出
2.1 将/etc/passwd文件导入MySQL数据库
2.1.1 新建userdb库、user表
mysql> CREATE DATABASE userdb;
mysql> USE userdb;
mysql> CREATE TABLE user(
-> name varchar(24) NOT NULL,
-> passwd varchar(48) DEFAULT 'x',
-> uid int(5) NOT NULL,
-> gid int(5) NOT NULL,
-> fullname varchar(128),
-> homedir varchar(64) NOT NULL,
-> shell varchar(24) NOT NULL
-> );
mysql> DESC user;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| name | varchar(24) | NO | | NULL | |
| passwd | varchar(48) | YES | | x | |
| uid | int(5) | NO | | NULL | |
| gid | int(5) | NO | | NULL | |
| fullname | varchar(128) | YES | | NULL | |
| homedir | varchar(64) | NO | | NULL | |
| shell | varchar(24) | NO | | NULL | |
+----------+-------------+------+-----+---------+-------+
2.1.2 查看mysql的工作文件夹
mysql> SHOW VARIABLES LIKE '%secure_file_priv';
+------------------+-----------------------+
| Variable_name | Value |
+------------------+-----------------------+
| secure_file_priv | /var/lib/mysql-files/ |
+------------------+-----------------------+
在MySQL 5.7.6版本之后，导入文件只能在secure_file_priv指定的文件夹下。
2.1.3 拷贝数据到目录
mysql> system cp /etc/passwd /var/lib/mysql-files/
mysql> LOAD DATA INFILE '/var/lib/mysql-files/passwd'
-> INTO TABLE user
-> FIELDS TERMINATED BY ':'
-> LINES TERMINATED BY '
';(这条默认有，除非用其他分隔用）
mysql> SELECT COUNT(*) FROM user;
+----------+
| COUNT(*) |
+----------+
| 42 |
+----------+
2.1.4 查看user前5条记录，列出用户名、UID
mysql> SELECT name ,uid FROM user LIMIT 5;
+--------+-----+
| name | uid |
+--------+-----+
| root | 0 |
| bin | 1 |
| daemon | 2 |
| adm | 3 |
| lp | 4 |
+--------+-----+
2.1.5 为user表中的每条记录添加自动编号
mysql> ALTER TABLE user ADD sn int(4) AUTO_INCREMENT PRIMARY KEY FIRST;
mysql> SELECT sn,name FROM user LIMIT 5;
+----+--------+
| sn | name |
+----+--------+
| 1 | root |
| 2 | bin |
| 3 | daemon |
| 4 | adm |
| 5 | lp |
+----+--------+
2.2 从MySQL数据库中导出查询结果
以将userdb库user表中UID小于100的前10条记录导出为/myload/user1.txt
2.2.1 修改默认目录
]# ls -ld /var/lib/mysql-files/
drwxr-x--- 2 mysql mysql 20 2月 13 15:10 /var/lib/mysql-files/
]# mkdir /myload
]# chown mysql /myload
]# ls -ld /myload
drwxr-xr-x 2 mysql root 6 2月 13 15:37 /myload
# vim /etc/my.cnf
[mysqld]
...
secure_file_priv="/myload"
]# systemctl restart mysqld
mysql> mysql> SHOW VARIABLES LIKE 'secure_file_priv';
2.2.2 导出user表中UID小于5的记录
如果以默认的'
' 为行分隔，导出操作同样可不指定LINES TERMINATED BY：
mysql> SELECT * FROM userdb.user1 WHERE uid<5;
+--------+--------+-----+-----+----------+----------------+---------------+
| name | passwd | uid | gid | fullname | homedir | shell |
+--------+--------+-----+-----+----------+----------------+---------------+
| root | x | 0 | 0 | root | /root | /bin/bash |
| bin | x | 1 | 1 | bin | /bin | /sbin/nologin |
| daemon | x | 2 | 2 | daemon | /sbin | /sbin/nologin |
| adm | x | 3 | 4 | adm | /var/adm | /sbin/nologin |
| lp | x | 4 | 7 | lp | /var/spool/lpd | /sbin/nologin |
+--------+--------+-----+-----+----------+----------------+---------------+
导出：
mysql> SELECT * FROM userdb.user1 WHERE uid<5
-> INTO OUTFILE '/myload/user1.txt'
-> FIELDS TERMINATED BY ':';
]# wc -l /myload/user1.txt
5 /myload/user1.txt
3.操作表记录
表记录的插入
表记录的更新
表记录的查询
表记录的删除
3.1 删除test.user1表的所有记录
mysql> DELETE FROM user1;
mysql> SELECT * FROM stu_info;
3.2 给t1插入三条数据
mysql> INSERT t1 VALUES
-> ('Jim','girl',24),
-> ('Tom','boy',21),
-> ('Lily','girl',20);
3.3 只插入部分字段的值
mysql> INSERT INTO t1(name,age)
-> VALUES('Jerry',27);
3.3 更新表记录时，若未限制条件，则适用于所有记录
mysql> UPDATE t1 SET age=10;
则所有人年龄都是10
3.4 更新表记录时，可以限制条件，只对符合条件的记录有效
mysql> UPDATE t1 SET age=20
-> WHERE gender='boy';
3.5 删除表记录时，可以限制条件，只删除符合条件的记录
mysql> DELETE FROM t1 WHERE age < 18;
3.6 删除表记录时，如果未限制条件，则会删除所有的表记录
mysql> DELETE FROM t1;
4.查询及匹配条件
4.1 查询stu_info表一共有多少条记录
mysql> SELECT count(*) FROM stu_info;
4.2 计算stu_info表中各学员的平均年龄、最大年龄、最小年龄
mysql> SELECT avg(age),max(age),min(age) FROM stu_info;
4.3 计算stu_info表中男学员的个数
mysql> SELECT count(gender) FROM stu_info WHERE gender='boy';
4.4 列出stu_info表中年龄为21岁的学员记录
mysql> SELECT * FROM stu_info WHERE age=21;
4.5 列出stu_info表中年龄超过21岁的学员记录
mysql> SELECT * FROM stu_info WHERE age>21;
4.6 列出stu_info表中年龄大于或等于21岁的学员记录
mysql> SELECT * FROM stu_info WHERE age>=21;
4.7 列出stu_info表中年龄在20岁和24岁之间的学员记录
mysql> SELECT * FROM stu_info WHERE age BETWEEN 20 and 24;
4.8 列出stu_info表中年龄小于23岁的女学员记录
mysql> SELECT * FROM stu_info WHERE age < 23 AND gender='girl';
4.9 列出stu_info表中年龄小于23岁的学员，或者女学员的记录：
mysql> SELECT * FROM stu_info WHERE age < 23 OR gender='girl';
4.10 如果某个记录的姓名属于指定范围内的一个，则将其列出
mysql> SELECT * FROM stu_info WHERE name IN
-> ('Jim','Tom','Mickey','Minnie');
4.11 计算1234与5678的和
mysql> SELECT 1234+5678;
4.12 输出stu_info表各学员的姓名、15年后的年龄
mysql> SELECT name,age+15 FROM stu_info;
4.13 列出stu_info表中姓名以“J”开头的学员记录
mysql> SELECT * FROM stu_info WHERE name LIKE 'J%';
4.14 列出stu_info表中姓名以“J”开头且只有3个字母的学员记录
mysql> SELECT * FROM stu_info WHERE name LIKE 'J__';
4.15 列出stu_info表中姓名以“J”开头且以“y”结尾的学员记录
mysql> SELECT * FROM stu_info WHERE name REGEXP '^J.*y$';
效果等同于：
mysql> SELECT * FROM stu_info WHERE name Like 'J%y';
4.16 列出stu_info表中姓名以“J”开头或者以“y”结尾的学员记录：
mysql> SELECT * FROM stu_info WHERE name REGEXP '^J|y$';
效果等同于：
mysql> SELECT * FROM stu_info WHERE name Like 'J%' OR name Like '%y';
4.17 列出stu_info表的所有记录，按年龄排序
mysql> SELECT * FROM stu_info GROUP BY age (ASC);(由小到大,默认)
mysql> SELECT * FROM stu_info GROUP BY age DESC;(由大到小）
4.18 限制查询结果的输出条数，LIMIT
mysql> SELECT * FROM stu_info LIMIT 3;
4.19 列出stu_info表中年龄最大的3条学员记录
mysql> SELECT * FROM stu_info GROUP BY age DESC LIMIT 3;
4.20 分组查询结果，GROUP BY
针对stu_info表，按性别分组，分别统计出男、女学员的人数：
mysql> SELECT gender,count(gender) FROM stu_info GROUP BY gender;
+--------+---------------+
| gender | count(gender) |
+--------+---------------+
| boy | 3 |
| girl | 2 |
+--------+---------------+
列出查询字段时，可以通过AS关键字来指定显示别名，比如上述操作可改为：
mysql> SELECT gender AS '性别',count(gender) AS '人数'
-> FROM stu_info GROUP BY gender;
+--------+--------+
| 性别 | 人数 |
+--------+--------+
| boy | 3 |
| girl | 2 |
+--------+--------+