开源数据库MYSQL DBA运维实战-SQL2语言

开源数据库MYSQL DBA运维实战-SQL2语言

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一.DML-操作语言

目的

在MySQL管理软件中，DDL已经定义了数据库结构。
那么如何对其中的数据进行管理呢？
可以通过SQL语句中的DML语言来实现数据的操作，包括使用

插入数据INSERT

完整插入

1.语法

insert into 表名 VALUES(值1,值2,值3…值n);

2.示例：

mysql> insert into student1 values (4,"laoliu","f",22);
Query OK, 1 row affected (0.00 sec)

查看所有数据
mysql> select * from student1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhangsan | m    |   33 |
|    2 | lisi     | f    |   23 |
|    3 | wangwu   | f    |   20 |
|    4 | laoliu   | f    |   22 |
+------+----------+------+------+
4 rows in set (0.00 sec)

部分插入

1.语法

insert into 表名（列名，列名） VALUES (值1,值2);

2.示例

mysql> insert into student1  (id)      values (5);
Query OK, 1 row affected (0.00 sec)

mysql> insert into student1  (id,name)   values (6,"yunjisuan");
Query OK, 1 row affected (0.01 sec)

mysql> insert into student1  (id,name,sex)   values (7,"liuzi","m");
Query OK, 1 row affected (0.01 sec)

查看表所有数据
mysql> select * from student1;
+------+-----------+------+------+
| id   | name      | sex  | age  |
+------+-----------+------+------+
|    1 | zhangsan  | m    |   33 |
|    2 | lisi      | f    |   23 |
|    3 | wangwu    | f    |   20 |
|    4 | laoliu    | f    |   22 |
|    5 | NULL      | NULL | NULL |
|    6 | yunjisuan | NULL | NULL |
|    7 | liuzi     | m    | NULL |
+------+-----------+------+------+
7 rows in set (0.00 sec)

更新数据UPDATE

1.语法

update 表名 set 列名=值 where condition;

2.示例

mysql> update student1 set name='kk' where id=5;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

查看表
mysql> select * from student1;
+------+-----------+------+------+
| id   | name      | sex  | age  |
+------+-----------+------+------+
|    1 | zhangsan  | m    |   33 |
|    2 | lisi      | f    |   23 |
|    3 | laoliu    | f    |   20 |
|    4 | laoliu    | f    |   22 |
|    5 | kk        | NULL | NULL |
|    6 | yunjisuan | NULL | NULL |
|    7 | liuzi     | m    | NULL |
+------+-----------+------+------+
7 rows in set (0.00 sec)

2.2示例二

修改mysql数据库管理员root账户的密码。

mysql> update mysql.user set authentication_string=password('XuShengKai@1234')  where user="root";
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1

缓存
mysql> \q
Bye

更新，此时密码已经修改完成

[root@192 ~]# mysql -uroot -p'XuShengKai@123'
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

更新完成后再次登录，登录密码就是修改过的密码

[root@192 ~]# mysql -uroot -p'XuShengKai@1234'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.7.36 MySQL Community Server (GPL)

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> 

删除数据

1.语法

delete from 表名 where condition;
如果不加where，整个表将会被删除

2.示例

mysql> delete from student1  where name='laoliu';
Query OK, 2 rows affected (0.00 sec)

查看结果
mysql> select * from student1;
+------+-----------+------+------+
| id   | name      | sex  | age  |
+------+-----------+------+------+
|    1 | zhangsan  | m    |   33 |
|    2 | lisi      | f    |   23 |
|    5 | kk        | NULL | NULL |
|    6 | yunjisuan | NULL | NULL |
|    7 | liuzi     | m    | NULL |
+------+-----------+------+------+
5 rows in set (0.00 sec)

二.DQL-查询语言

概述

在MySQL管理软件中，可以通过SQL语句中的DQL语言来实现数据的SELECT 查询操作
互联网用户查询余额，查询装备，查询商品的操作。

准备测试环境

准备一张表

id int 序号
name varchar 姓名
age int 年龄

mysql> create   table   t3   (id   int,name   varchar(20),age  int);
Query OK, 0 rows affected (0.00 sec)

1.插入数据

mysql> insert   into   t3   values  (1,"zhangsan",23);
Query OK, 1 row affected (0.00 sec)

mysql> insert   into   t3   values  (2,"lisi",24);
Query OK, 1 row affected (0.00 sec)

mysql> insert   into   t3   values  (3,"wangwu",18);
Query OK, 1 row affected (0.00 sec)

查看结果
mysql> select * from t3;
+------+----------+------+
| id   | name     | age  |
+------+----------+------+
|    1 | zhangsan |   23 |
|    2 | lisi     |   24 |
|    3 | wangwu   |   18 |
+------+----------+------+
3 rows in set (0.01 sec)

准备第二张表

1.创建表

mysql> create database company;
Query OK, 1 row affected (0.01 sec)

2.创建数据表

mysql>  CREATE TABLE company.employee5(
    ->      id int primary key AUTO_INCREMENT not null,
    ->     name varchar(30) not null,
    ->     sex enum('male','female') default 'male' not null,
    ->      hire_date date not null,
    ->      post varchar(50) not null,
    ->      job_description varchar(100),
    ->      salary double(15,2) not null,
    ->      office int,
    ->      dep_id int
    ->      );
Query OK, 0 rows affected (0.00 sec)
格式这个样子是因为数据库的语言，把每一列都敲成一行,看起来舒服一点

3.插入数据

mysql> insert into company.employee5(name,sex,hire_date,post,job_description,salary,office,dep_id) values 
    -> ('jack','male','20180202','instructor','teach',5000,501,100),
    -> ('tom','male','20180203','instructor','teach',5500,501,100),
    -> ('robin','male','20180202','instructor','teach',8000,501,100),
    -> ('alice','female','20180202','instructor','teach',7200,501,100),
    -> ('aofa','male','20180202','hr','hrcc',600,502,101),
    -> ('harry','male','20180202','hr',NULL,6000,502,101),
    -> ('emma','female','20180206','sale','salecc',20000,503,102), 
    -> ('christine','female','20180205','sale','salecc',2200,503,102),
    -> ('zhuzhu','male','20180205','sale',NULL,2200,503,102),
    -> ('gougou','male','20180205','sale','',2200,503,102);
Query OK, 10 rows affected (0.00 sec)
Records: 10  Duplicates: 0  Warnings: 0

查询所有数据

简单查询

查看所有列,前提是需要进入数据库。不进入数据库，就请输入库名。
语法：SELECT * FROM 表名;
查部分列
语法：SELECT 列1，列2，列3 FROM 表名;

1.查看所有列

mysql> select * from company.employee5;
+----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
| id | name      | sex    | hire_date  | post       | job_description | salary   | office | dep_id |
+----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
|  1 | jack      | male   | 2018-02-02 | instructor | teach           |  5000.00 |    501 |    100 |
|  2 | tom       | male   | 2018-02-03 | instructor | teach           |  5500.00 |    501 |    100 |
|  3 | robin     | male   | 2018-02-02 | instructor | teach           |  8000.00 |    501 |    100 |
|  4 | alice     | female | 2018-02-02 | instructor | teach           |  7200.00 |    501 |    100 |
|  5 | aofa      | male   | 2018-02-02 | hr         | hrcc            |   600.00 |    502 |    101 |
|  6 | harry     | male   | 2018-02-02 | hr         | NULL            |  6000.00 |    502 |    101 |
|  7 | emma      | female | 2018-02-06 | sale       | salecc          | 20000.00 |    503 |    102 |
|  8 | christine | female | 2018-02-05 | sale       | salecc          |  2200.00 |    503 |    102 |
|  9 | zhuzhu    | male   | 2018-02-05 | sale       | NULL            |  2200.00 |    503 |    102 |
| 10 | gougou    | male   | 2018-02-05 | sale       |                 |  2200.00 |    503 |    102 |
+----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
10 rows in set (0.00 sec)

2.查询部分列

mysql> select  id,name from company.employee5;
+----+-----------+
| id | name      |
+----+-----------+
|  1 | jack      |
|  2 | tom       |
|  3 | robin     |
|  4 | alice     |
|  5 | aofa      |
|  6 | harry     |
|  7 | emma      |
|  8 | christine |
|  9 | zhuzhu    |
| 10 | gougou    |
+----+-----------+
10 rows in set (0.00 sec)

3.通过四则运算查询，看看年薪

mysql> show databases;   #查看库

mysql> use company  #进入库

mysql> select name,salary,salary*14 from employee5;
+-----------+----------+-----------+
| name      | salary   | salary*14 |
+-----------+----------+-----------+
| jack      |  5000.00 |  70000.00 |
| tom       |  5500.00 |  77000.00 |
| robin     |  8000.00 | 112000.00 |
| alice     |  7200.00 | 100800.00 |
| aofa      |   600.00 |   8400.00 |
| harry     |  6000.00 |  84000.00 |
| emma      | 20000.00 | 280000.00 |
| christine |  2200.00 |  30800.00 |
| zhuzhu    |  2200.00 |  30800.00 |
| gougou    |  2200.00 |  30800.00 |
+-----------+----------+-----------+
10 rows in set (0.00 sec)

条件查询where

1.语法：如果不写库名，得先进入库

select 列名 from 表名 where 条件;

2.查询hr部门的员工姓名

mysql> select name from employee5 where post="hr";
+-------+
| name  |
+-------+
| aofa  |
| harry |
+-------+
2 rows in set (0.00 sec)

单条件查询and/or

1.语法

select 列名 from 表名 where 条件 and 条件;

2.查询hr部门的员工姓名，并且工资大于1000

mysql> select *  from employee5 where post="hr" and salary>1000;
+----+-------+------+------------+------+-----------------+---------+--------+--------+
| id | name  | sex  | hire_date  | post | job_description | salary  | office | dep_id |
+----+-------+------+------------+------+-----------------+---------+--------+--------+
|  6 | harry | male | 2018-02-02 | hr   | NULL            | 6000.00 |    502 |    101 |
+----+-------+------+------------+------+-----------------+---------+--------+--------+
1 row in set (0.00 sec)

3.查询所有部门的员工姓名，并且工资是6000的员工或者8000的员工

mysql> select *  from employee5 where salary=6000 or salary>8000;
+----+-------+--------+------------+------+-----------------+----------+--------+--------+
| id | name  | sex    | hire_date  | post | job_description | salary   | office | dep_id |
+----+-------+--------+------------+------+-----------------+----------+--------+--------+
|  6 | harry | male   | 2018-02-02 | hr   | NULL            |  6000.00 |    502 |    101 |
|  7 | emma  | female | 2018-02-06 | sale | salecc          | 20000.00 |    503 |    102 |
+----+-------+--------+------------+------+-----------------+----------+--------+--------+
2 rows in set (0.00 sec)

关键字between and在什么之间

1.语法

select 列名 from 表名 where 条件 （not可选）between 范围 and 范围;

2.查一查薪资在5000到15000

mysql> select name,salary from employee5 where salary between 5000 and 15000;
+-------+---------+
| name  | salary  |
+-------+---------+
| jack  | 5000.00 |
| tom   | 5500.00 |
| robin | 8000.00 |
| alice | 7200.00 |
| harry | 6000.00 |
+-------+---------+
5 rows in set (0.00 sec)

3.不在5000~15000呢？请使用NOT

mysql> select name,salary from employee5 where salary not between 5000 and 15000;
+-----------+----------+
| name      | salary   |
+-----------+----------+
| aofa      |   600.00 |
| emma      | 20000.00 |
| christine |  2200.00 |
| zhuzhu    |  2200.00 |
| gougou    |  2200.00 |
+-----------+----------+
5 rows in set (0.00 sec)

关键字in集合查询

1.语法

select 列名 from 表名 where 条件 in (关键字);

2.查询工资可能是4000，也可能是5000，还有可能是9000。

mysql> select * from employee5 where salary in (4000,5000,6000,20000); 
+----+-------+--------+------------+------------+-----------------+----------+--------+--------+
| id | name  | sex    | hire_date  | post       | job_description | salary   | office | dep_id |
+----+-------+--------+------------+------------+-----------------+----------+--------+--------+
|  1 | jack  | male   | 2018-02-02 | instructor | teach           |  5000.00 |    501 |    100 |
|  6 | harry | male   | 2018-02-02 | hr         | NULL            |  6000.00 |    502 |    101 |
|  7 | emma  | female | 2018-02-06 | sale       | salecc          | 20000.00 |    503 |    102 |
+----+-------+--------+------------+------------+-----------------+----------+--------+--------+
3 rows in set (0.00 sec)

3.取反，加not

mysql> select * from employee5 where salary not in (4000,5000,6000,200000);
+----+-----------+--------+------------+------------+-----------------+---------+--------+--------+
| id | name      | sex    | hire_date  | post       | job_description | salary  | office | dep_id |
+----+-----------+--------+------------+------------+-----------------+---------+--------+--------+
|  2 | tom       | male   | 2018-02-03 | instructor | teach           | 5500.00 |    501 |    100 |
|  3 | robin     | male   | 2018-02-02 | instructor | teach           | 8000.00 |    501 |    100 |
|  4 | alice     | female | 2018-02-02 | instructor | teach           | 7200.00 |    501 |    100 |
|  5 | aofa      | male   | 2018-02-02 | hr         | hrcc            |  600.00 |    502 |    101 |
|  8 | christine | female | 2018-02-05 | sale       | salecc          | 2200.00 |    503 |    102 |
|  9 | zhuzhu    | male   | 2018-02-05 | sale       | NULL            | 2200.00 |    503 |    102 |
| 10 | gougou    | male   | 2018-02-05 | sale       |                 | 2200.00 |    503 |    102 |
+----+-----------+--------+------------+------------+-----------------+---------+--------+--------+
7 rows in set (0.00 sec)

关键字is null

1.语法：没有写东西的空的

select 列名 from 表名 where 条件 is （not可选，取反）null;

2.没有岗位描述的job_description

mysql> select * from employee5 where job_description is null;
+----+--------+------+------------+------+-----------------+---------+--------+--------+
| id | name   | sex  | hire_date  | post | job_description | salary  | office | dep_id |
+----+--------+------+------------+------+-----------------+---------+--------+--------+
|  6 | harry  | male | 2018-02-02 | hr   | NULL            | 6000.00 |    502 |    101 |
|  9 | zhuzhu | male | 2018-02-05 | sale | NULL            | 2200.00 |    503 |    102 |
+----+--------+------+------------+------+-----------------+---------+--------+--------+
2 rows in set (0.00 sec)

关键字LIKE模糊查询

1.语法

select 列名 from 表名 where 列名 like ‘条件%’;
这里%是任意的意思，在mysql中用%来代表任意的意思，放在前面就是以什么结尾的，放在后面就是以什么开头的
select 列名 from employee5 where 列名 like ‘条件_’;
mysql使用下划线，通配符"_"代表任意1个字符，写几个下划线就代表几个。

2.查找名字以a开头的员工

mysql> select * from employee5 where name like 'a%';
+----+-------+--------+------------+------------+-----------------+---------+--------+--------+
| id | name  | sex    | hire_date  | post       | job_description | salary  | office | dep_id |
+----+-------+--------+------------+------------+-----------------+---------+--------+--------+
|  4 | alice | female | 2018-02-02 | instructor | teach           | 7200.00 |    501 |    100 |
|  5 | aofa  | male   | 2018-02-02 | hr         | hrcc            |  600.00 |    502 |    101 |
+----+-------+--------+------------+------------+-----------------+---------+--------+--------+
2 rows in set (0.00 sec)

2.2查找名字是alice的员工，四个下划线

mysql> select * from employee5 where name like 'a____';
+----+-------+--------+------------+------------+-----------------+---------+--------+--------+
| id | name  | sex    | hire_date  | post       | job_description | salary  | office | dep_id |
+----+-------+--------+------------+------------+-----------------+---------+--------+--------+
|  4 | alice | female | 2018-02-02 | instructor | teach           | 7200.00 |    501 |    100 |
+----+-------+--------+------------+------------+-----------------+---------+--------+--------+
1 row in set (0.00 sec)

2.3查找名字是aofa的员工,三个下划线

mysql> select * from employee5 where name like 'a___';
+----+------+------+------------+------+-----------------+--------+--------+--------+
| id | name | sex  | hire_date  | post | job_description | salary | office | dep_id |
+----+------+------+------------+------+-----------------+--------+--------+--------+
|  5 | aofa | male | 2018-02-02 | hr   | hrcc            | 600.00 |    502 |    101 |
+----+------+------+------------+------+-----------------+--------+--------+--------+
1 row in set (0.00 sec)

查询排序

1.语法

select 列名 from 表名 order by 列名 asc/desc;
order排序的意思，不加asc和desc默认升序
asc升序
deac降序，工作中常用

2.工资升序排列

mysql> select name,salary from employee5 order by salary asc;
+-----------+----------+
| name      | salary   |
+-----------+----------+
| aofa      |   600.00 |
| christine |  2200.00 |
| zhuzhu    |  2200.00 |
| gougou    |  2200.00 |
| jack      |  5000.00 |
| tom       |  5500.00 |
| harry     |  6000.00 |
| alice     |  7200.00 |
| robin     |  8000.00 |
| emma      | 20000.00 |
+-----------+----------+
10 rows in set (0.00 sec)

3.工资最高前五名

mysql> select name,salary from employee5 order by salary desc limit 5; 
+-------+----------+
| name  | salary   |
+-------+----------+
| emma  | 20000.00 |
| robin |  8000.00 |
| alice |  7200.00 |
| harry |  6000.00 |
| tom   |  5500.00 |
+-------+----------+
5 rows in set (0.00 sec)

参数解释：
limit：限制，限制几后面就写几