说明：本文旨在记录常见数据库操作
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数据库相关
-
增加数据库;
create database 数据库的名字 charset=字符编码;create database testdb charset=utf8; -
查询数据库
show databases;mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mock_db | | mysql | | performance_schema | | sys | | testdb | +--------------------+ 6 rows in set (0.01 sec) -
选择数据库
use testdb;mysql> use testdb; Database changed mysql> -
查看正在使用的数据库
select database();mysql> select database(); +------------+ | database() | +------------+ | testdb | +------------+ 1 row in set (0.00 sec) mysql> -
查看使用的数据库的所有表
show tables;mysql> show tables; Empty set (0.00 sec) mysql> -
删除数据库
drop database 数据库名称;mysql> drop database testdb; Query OK, 0 rows affected (0.00 sec) mysql> -
数据库备份
这里用到的是终端的一个重定向
>的命令Mac下数据库的数据保存的路径/usr/local/mysql/data进入上面目录
sudo cd /usr/local/mysql/data使用
mysqldump命令将数据备份到桌面下~/Desktop/kkk.sql➜ ~ mysqldump -u root -p testdb > ~/Desktop/kkk.sql; Enter password:数据密码就可以在桌面看到kkk.sql了
我们先把旧的
testdb删除掉drop database testdb;查看一下
mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mock_db | | mysql | | performance_schema | | sys | +--------------------+ 5 rows in set (0.00 sec) mysql>我们来创建一个空的名为
testdb的数据库create database testdb2 charset=utf8;我们查看下
testdb
```
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mock_db |
| mysql |
| performance_schema |
| sys |
| testdb |
+--------------------+
6 rows in set (0.00 sec)
mysql> use testdb;
Database changed
mysql> show tables;
Empty set (0.00 sec)
```
恢复数据
```
➜ ~ mysql -u root -p testdb < ~/Desktop/kkk.sql;
Enter password:
```
再查一次
```
mysql> show tables;
+------------------+
| Tables_in_testdb |
+------------------+
| person |
+------------------+
1 row in set (0.00 sec)
mysql> select *from person;
+----+----------------+------+
| id | name | city |
+----+----------------+------+
| 1 | zhangsanfeng | |
| 3 | zhaomin | |
| 4 | xiaozhao | |
| 5 | jinnmaoshiwang | |
| 6 | baimei | |
+----+----------------+------+
5 rows in set (0.00 sec)
mysql>
```
表相关
-
增加表
create table 表名(列及类型);mysql> create table person( > id int auto_increment primary key, > name varchar(20) not null); Query OK, 0 rows affected (0.02 sec)通过
show tables查看mysql> show tables; +------------------+ | Tables_in_testdb | +------------------+ | person | +------------------+ 1 row in set (0.00 sec) mysql> -
查看表属性信息
desc 表名称;mysql> desc person; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | NO | | NULL | | +-------+-------------+------+-----+---------+----------------+ 2 rows in set (0.00 sec) mysql> -
删除表
drop table 表名;现在有2张表
mysql> show tables; +------------------+ | Tables_in_testdb | +------------------+ | person | | test2 | +------------------+ 2 rows in set (0.00 sec)删除
test2表mysql> drop table test2; Query OK, 0 rows affected (0.00 sec) mysql> show tables; +------------------+ | Tables_in_testdb | +------------------+ | person | +------------------+ 1 row in set (0.00 sec) -
修改表
alter table 表名 add | change | drop 列名 类型;比如：
将
person表的gender 改成gender2;alter table person change gender gender2 bit;给person增加
city列alter table person add city varchar(20);删除person的gender2
alter table person drop gender2;
数据相关
-
查询表数据
select * from 表名; -
添加数据
(1). 全列增加单个：
insert into 表名 values(...);mysql> insert into person values(0,'zhangsanfeng'); Query OK, 1 row affected (0.01 sec) mysql>查询结果
mysql> select * from person; +----+--------------+ | id | name | +----+--------------+ | 1 | zhangsanfeng | +----+--------------+ 1 row in set (0.00 sec) mysql>(2). 全列增加多个：
insert into 表名 values(...),(...);mysql> insert into person values(0,'zhangwuji'),(0,'zhaomin'); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0查看一下
mysql> select * from person; +----+--------------+ | id | name | +----+--------------+ | 1 | zhangsanfeng | | 2 | zhangwuji | | 3 | zhaomin | +----+--------------+ 3 rows in set (0.00 sec) mysql>(3). 单列增加单个：
insert into 表名(列名) values(...);mysql> insert into person(name) values('xiaozhao'); Query OK, 1 row affected (0.01 sec)查看
mysql> select * from person; +----+--------------+ | id | name | +----+--------------+ | 1 | zhangsanfeng | | 2 | zhangwuji | | 3 | zhaomin | | 4 | xiaozhao | +----+--------------+ 4 rows in set (0.00 sec) mysql>(4). 单列增加多个：
insert into 表名(列名) values(...),values(...);mysql> insert into person(name) values('jinnmaoshiwang'),('zhangcuishan'); Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0查看
```
mysql> select * from person;
+----+----------------+
| id | name |
+----+----------------+
| 1 | zhangsanfeng |
| 2 | zhangwuji |
| 3 | zhaomin |
| 4 | xiaozhao |
| 5 | jinnmaoshiwang |
| 6 | zhangcuishan |
+----+----------------+
6 rows in set (0.00 sec)
mysql>
```
-
更新数据
update 表名 set 列名=值 where 条件mysql> update person set name='baimei' where id=6; Query OK, 1 row affected (0.01 sec) Rows matched: 1 Changed: 1 Warnings: 0查看
mysql> select *from person; +----+----------------+ | id | name | +----+----------------+ | 1 | zhangsanfeng | | 2 | zhangwuji | | 3 | zhaomin | | 4 | xiaozhao | | 5 | jinnmaoshiwang | | 6 | baimei | +----+----------------+ 6 rows in set (0.00 sec) mysql> -
删除数据
delete from 表名 where 条件在person表中删除id为2的数据
mysql> delete from person where id=2; Query OK, 1 row affected (0.01 sec)查看
mysql> select *from person; +----+----------------+ | id | name | +----+----------------+ | 1 | zhangsanfeng | | 3 | zhaomin | | 4 | xiaozhao | | 5 | jinnmaoshiwang | | 6 | baimei | +----+----------------+ 5 rows in set (0.00 sec) mysql>
常见数据查询操作
1. 模糊查询
- like
- %表示任意多个，也即是可有可无
- _表示一个任意字符，至少一个
person表内容
mysql> select * from person;
+----+----------------+----------+
| id | name | city |
+----+----------------+----------+
| 1 | zhangsanfeng | Shanghai |
| 3 | zhaomin | 北京 |
| 4 | xiaozhao | |
| 5 | jinnmaoshiwang | 北京 |
| 6 | baimei | |
+----+----------------+----------+
5 rows in set (0.00 sec)
mysql>
查询城市是北京的人的名字
mysql> select name from person where city like '北京';
+----------------+
| name |
+----------------+
| zhaomin |
| jinnmaoshiwang |
+----------------+
2 rows in set (0.01 sec)
mysql>
查询以北开头的人的名字，使用%和_都可以
mysql> select name from person where city like '北%';
+----------------+
| name |
+----------------+
| zhaomin |
| jinnmaoshiwang |
+----------------+
2 rows in set (0.00 sec)
mysql> select name from person where city like '北_';
+----------------+
| name |
+----------------+
| zhaomin |
| jinnmaoshiwang |
+----------------+
2 rows in set (0.00 sec)
修改一下zhaomin的city区分一下%和_;
mysql> update person set city='北' where id=3;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from person;
+----+----------------+----------+
| id | name | city |
+----+----------------+----------+
| 1 | zhangsanfeng | Shanghai |
| 3 | zhaomin | 北 |
| 4 | xiaozhao | |
| 5 | jinnmaoshiwang | 北京 |
| 6 | baimei | |
+----+----------------+----------+
5 rows in set (0.00 sec)
再运行下上面的
mysql> select name from person where city like '北%';
+----------------+
| name |
+----------------+
| zhaomin |
| jinnmaoshiwang |
+----------------+
2 rows in set (0.00 sec)
mysql>
mysql> select name from person where city like '北_';
+----------------+
| name |
+----------------+
| jinnmaoshiwang |
+----------------+
1 row in set (0.00 sec)
2. 聚合查询
| 简写 | 含义 |
|---|---|
| min | 最小值 |
| max | 最大值 |
| avg | 平均值 |
| sum | 求和 |
| count | 数量 |
mysql> select *from person;
+----+----------------+--------+
| id | name | city |
+----+----------------+--------+
| 1 | zhangsanfeng | 上海 |
| 3 | zhaomin | 北 |
| 4 | xiaozhao | 上海 |
| 5 | jinnmaoshiwang | 北京 |
| 6 | baimei | 上海 |
+----+----------------+--------+
5 rows in set (0.00 sec)
求city是上海的人的总和
mysql> select count(*) from person where city='上海';
+----------+
| count(*) |
+----------+
| 3 |
+----------+
1 row in set (0.01 sec)
求city是上海的人中id最大的的人
mysql> select max(id) from person where city='上海';
+---------+
| max(id) |
+---------+
| 6 |
+---------+
1 row in set (0.01 sec)
其他的和上面的类似
3. 分组查询
查询每个city的人的总数
mysql> select city ,count(*) from person group by city;
+--------+----------+
| city | count(*) |
+--------+----------+
| 上海 | 3 |
| 北 | 1 |
| 北京 | 1 |
+--------+----------+
对结果进行排序,使用order by
将上面的结果按照总数进行，升序排序
mysql> select city ,count(*) as 总数 from person group by city order by 总数 asc;
+--------+--------+
| city | 总数 |
+--------+--------+
| 北 | 1 |
| 北京 | 1 |
| 上海 | 3 |
+--------+--------+
3 rows in set (0.00 sec)
上面的as是取别名
单独看上海的有多少人，使用having
mysql> select city ,count(*) from person group by city having city='上海';
+--------+----------+
| city | count(*) |
+--------+----------+
| 上海 | 3 |
+--------+----------+
1 row in set (0.00 sec)
分页查询，使用limit
select * from 表名 limit start,count
start，表示从第几个元素开始；
count，查询几个
mysql> select * from person;
+----+----------------+--------+
| id | name | city |
+----+----------------+--------+
| 1 | zhangsanfeng | 上海 |
| 3 | zhaomin | 北 |
| 4 | xiaozhao | 上海 |
| 5 | jinnmaoshiwang | 北京 |
| 6 | baimei | 上海 |
| 7 | zhangsan1 | 海南 |
| 8 | zhangsan2 | 海南 |
| 9 | zhangsan3 | 海南 |
| 10 | zhangsan4 | 海南 |
| 11 | zhangsan5 | 海南 |
| 12 | zhangsan6 | 海南 |
| 13 | zhangsan7 | 海南 |
| 14 | zhangsan8 | 海南 |
+----+----------------+--------+
13 rows in set (0.00 sec)
需求：分页查找，每页2个，从0开始；
第一页
mysql> select * from person limit 0,3;
+----+--------------+--------+
| id | name | city |
+----+--------------+--------+
| 1 | zhangsanfeng | 上海 |
| 3 | zhaomin | 北 |
| 4 | xiaozhao | 上海 |
+----+--------------+--------+
3 rows in set (0.00 sec)
第二页
mysql> select * from person limit 3,3;
+----+----------------+--------+
| id | name | city |
+----+----------------+--------+
| 5 | jinnmaoshiwang | 北京 |
| 6 | baimei | 上海 |
| 7 | zhangsan1 | 海南 |
+----+----------------+--------+
3 rows in set (0.00 sec)
第三页
mysql> select * from person limit 6,3;
+----+-----------+--------+
| id | name | city |
+----+-----------+--------+
| 8 | zhangsan2 | 海南 |
| 9 | zhangsan3 | 海南 |
| 10 | zhangsan4 | 海南 |
+----+-----------+--------+
3 rows in set (0.00 sec)
having和where区别
where是对原始数据进行筛选；
having是对筛选的结果进行筛选。
该文会持续补充。。。
