mysql数据库学习笔记之常用操作命令_MySQL

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mysql数据库学习笔记之常用操作命令

 

1、创建数据库    

mysql> create database user;

Query OK, 1 row affected (0.00 sec)

2、使用此数据库

mysql> use user;

Database changed

3、在此数据库上创建表

mysql> create table person(

    -> id int unsigned not null auto_increment primary key,

    -> name varchar(30)

    -> );                  

Query OK, 0 rows affected (0.00 sec)

4、查看此person表的表结构    

mysql> desc person;

+-------+------------------+------+-----+---------+----------------+

| Field | Type             | Null | Key | Default | Extra          |

+-------+------------------+------+-----+---------+----------------+

| id    | int(10) unsigned | NO   | PRI | NULL    | auto_increment |

| name  | varchar(30)      | YES  |     | NULL    |                |

+-------+------------------+------+-----+---------+----------------+

2 rows in set (0.00 sec)

5、创建person_bak,并是此表的表结构与person一样，即复制person的表结构

mysql> create table person_bak like person;

Query OK, 0 rows affected (0.01 sec)

 

6、向person表中插入数据

mysql> insert into person (name) values ("user1");

Query OK, 1 row affected (0.00 sec)

7、将person表中的数据复制到person_bak表中

mysql> insert into person_bak select * from person;

Query OK, 10 rows affected (0.01 sec)

Records: 10  Duplicates: 0  Warnings: 0

 

8、向person表中创建name列的索引

方法一：

mysql> create index in_name on person (name);

Query OK, 10 rows affected (0.00 sec)

Records: 10  Duplicates: 0  Warnings: 0

方法二：

mysql> alter table person add index in_name (name);

Query OK, 10 rows affected (0.01 sec)

Records: 10  Duplicates: 0  Warnings: 0

9、查看索引    

mysql> show index from person;

+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+

| Table  | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |

+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+

| person |          0 | PRIMARY  |            1 | id          | A         |          10 |     NULL | NULL   |      | BTREE      |         |

| person |          1 | in_name  |            1 | name        | A         |        NULL |     NULL | NULL   | YES  | BTREE      |         |

+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+

2 rows in set (0.01 sec)

 

10、在person表中创建唯一索引

mysql> alter table person add unique index un_name (name);

Query OK, 10 rows affected (0.01 sec)

Records: 10  Duplicates: 0  Warnings: 0

11、修改列的属性

mysql> alter table person modify name varchar(20);

Query OK, 10 rows affected (0.01 sec)

Records: 10  Duplicates: 0  Warnings: 0

12、统计表中的数据数据

mysql> select count(*) from person;

+----------+

| count(*) |

+----------+

|       10 |

+----------+

1 row in set (0.00 sec)

13、创建一个视图

mysql> create view v_person as select * from person;

Query OK, 0 rows affected (0.01 sec)

14、查看视图(和查看表的命令一样)

当删除表中的某条记录时，相应的此表对应的视图中的满足条件的记录也将会被删除掉

mysql> show tables;

+----------------+

| Tables_in_user |

+----------------+

| person         |

| person_bak     |

| v_person       |

+----------------+

3 rows in set (0.00 sec)

15、删除视图

mysql> drop view v_person;

Query OK, 0 rows affected (0.00 sec)

16、字符串连接函数---concat("string1","string2") 别名

mysql> select concat("li","haichao") myname;

+-----------+

| myname    |

+-----------+

| lihaichao |

+-----------+

1 row in set (0.00 sec)

17、大写转换成小写的函数---lcase(string1)

mysql> select lcase("LHC");

+--------------+

| lcase("LHC") |

+--------------+

| lhc          |

+--------------+

1 row in set (0.00 sec)

18、将字符串转换成大写的函数----ucase(string1);

mysql> select ucase("lhc");

+--------------+

| ucase("lhc") |

+--------------+

| LHC          |

+--------------+

1 row in set (0.00 sec)

19、判断字符串长度的函数length(string1);

mysql> select length("lhc");

+---------------+

| length("lhc") |

+---------------+

|             3 |

+---------------+

1 row in set (0.02 sec)

20、去除前端和后端的空格函数 ltrim()和rtrim()

21、将指定的字符串重复n次，repeat(string ,count)

mysql> select repeat("linux",3);

+-------------------+

| repeat("linux",3) |

+-------------------+

| linuxlinuxlinux   |

+-------------------+

1 row in set (0.02 sec)

22、字符串替换函数

在"linux is very good"中寻找linux，并将其替换成php

mysql> select replace("linux is very good","linux","php");

+---------------------------------------------+

| replace("linux is very good","linux","php") |

+---------------------------------------------+

| php is very good                            |

+---------------------------------------------+

1 row in set (0.01 sec)

23、字符串截取函数substring("str",int 1,int 2)

在str字符串中从int1开始(从1计)到int2结束(包含),取其字段

mysql> select substring("linux is very good",1,5);

+-------------------------------------+

| substring("linux is very good",1,5) |

+-------------------------------------+

| linux                               |

+-------------------------------------+

1 row in set (0.00 sec)

24、space(）函数：生成空格的函数，通常与concat函数一起使用

 

mysql> select concat(space(50),"linux");

+---------------------------------------------------------+

| concat(space(50),"linux")                               |

+---------------------------------------------------------+

|                                                   linux |

+---------------------------------------------------------+

1 row in set (0.02 sec)

25、十进制转二进制函数BIN()

mysql> select BIN(255);

+----------+

| BIN(255) |

+----------+

| 11111111 |

+----------+

1 row in set (0.00 sec)

26、向上取整函数CEILING()，比如5.6则为6，向下取整floor(),比如5.6则为5

mysql> select ceiling(5.6);

+--------------+

| ceiling(5.6) |

+--------------+

|            6 |

+--------------+

1 row in set (0.01 sec)

************************************************************************

mysql> select floor(5.6);

+------------+

| floor(5.6) |

+------------+

|          5 |

+------------+

1 row in set (0.00 sec)

27、取最大值和最小值

select sutdent_name,MIN(test_score),MAX(test_score) from student group by student_name;

28、返回随机数:RAND()

mysql> select ceiling( 10*RAND());

+---------------------+

| ceiling( 10*RAND()) |

+---------------------+

|                   4 |

+---------------------+

1 row in set (0.00 sec)

 

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