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Mysql 常用命令

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标签:hone   where   cti   delete   偏移量   limit   size   phone   0.11   

一、Mysql 创建数据库 

mysql> create database study charset utf8;
Query OK, 1 row affected (0.01 sec)

 

二、创建数据表

  语法:

CREATE TABLE table_name (column_name column_type);

  创建一个student表

mysql> create table student(
    -> stu_id int NOT NULL AUTO_INCREMENT,               
    -> name char(32) NOT NULL,
    -> age int NOT NULL,
    -> register_date DATE NOT NULL,
    -> primary key (stu_id)
    -> );
Query OK, 0 rows affected (0.02 sec)



mysql> desc student;
+---------------+----------+------+-----+---------+----------------+
| Field         | Type     | Null | Key | Default | Extra          |
+---------------+----------+------+-----+---------+----------------+
| stu_id        | int(11)  | NO   | PRI | NULL    | auto_increment |
| name          | char(32) | NO   |     | NULL    |                |
| age           | int(11)  | NO   |     | NULL    |                |
| register_date | date     | NO   |     | NULL    |                |
+---------------+----------+------+-----+---------+----------------+
4 rows in set (0.01 sec)
  • 如果你不想字段为 NULL 可以设置字段的属性为 NOT NULL, 在操作数据库时如果输入该字段的数据为NULL ,就会报错。
  • AUTO_INCREMENT定义列为自增的属性,一般用于主键,数值会自动加1。
  • PRIMARY KEY关键字用于定义列为主键。 您可以使用多列来定义主键,列间以逗号分隔。

 

三、数据操作

  3.1 插入数据

  语法:  

INSERT INTO table_name ( field1, field2,...fieldN )
                       VALUES
                       ( value1, value2,...valueN );

  插入数据:

mysql> insert into student (name,age,register_date) values (‘bigberg‘,11,‘2018-01-01‘);
Query OK, 1 row affected (0.01 sec)

mysql> select * from student;
+--------+---------+-----+---------------+
| stu_id | name    | age | register_date |
+--------+---------+-----+---------------+
|      1 | bigberg |  11 | 2018-01-01    |
+--------+---------+-----+---------------+
1 row in set (0.00 sec)

  3.2 查询数据

  语法:

SELECT column_name,column_name
FROM table_name
[WHERE Clause]
[OFFSET M ][LIMIT N]
  • 查询语句中你可以使用一个或者多个表,表之间使用逗号(,)分割,并使用WHERE语句来设定查询条件。
  • SELECT 命令可以读取一条或者多条记录。
  • 你可以使用星号(*)来代替其他字段,SELECT语句会返回表的所有字段数据
  • 你可以使用 WHERE 语句来包含任何条件。
  • 你可以通过OFFSET指定SELECT语句开始查询的数据偏移量。默认情况下偏移量为0, 如果使用不能单独使用。
  • 你可以使用 LIMIT 属性来设定返回的记录数。
select * from student;

select * from student where stu_id > 2;

select * from student where register_date like ‘2018-02-%‘;
mysql> select * from student limit 3, 1;
+--------+--------+-----+---------------+
| stu_id | name   | age | register_date |
+--------+--------+-----+---------------+
|      4 | wangwu |  23 | 2018-02-14    |
+--------+--------+-----+---------------+
1 row in set (0.00 sec)


# limit后面是从第3条开始读,读取1条信息。
mysql> select * from student limit 3 offset 2;
+--------+--------+-----+---------------+
| stu_id | name   | age | register_date |
+--------+--------+-----+---------------+
|      3 | lisi   |  31 | 2018-02-11    |
|      4 | wangwu |  23 | 2018-02-14    |
+--------+--------+-----+---------------+
2 rows in set (0.00 sec)

# limit后面跟的是3条数据,offset后面是从第3条开始读取

  3.3 where 字句

   语法:

SELECT field1, field2,...fieldN FROM table_name1, table_name2...
[WHERE condition1 [AND [OR]] condition2.....  
操作符描述实例
= 等号,检测两个值是否相等,如果相等返回true (A = B) 返回false。
<>, != 不等于,检测两个值是否相等,如果不相等返回true (A != B) 返回 true。
> 大于号,检测左边的值是否大于右边的值, 如果左边的值大于右边的值返回true (A > B) 返回false。
< 小于号,检测左边的值是否小于右边的值, 如果左边的值小于右边的值返回true (A < B) 返回 true。
>= 大于等于号,检测左边的值是否大于或等于右边的值, 如果左边的值大于或等于右边的值返回true (A >= B) 返回false。
<= 小于等于号,检测左边的值是否小于于或等于右边的值, 如果左边的值小于或等于右边的值返回true (A <= B) 返回 true。

  使用主键来作为 WHERE 子句的条件查询是非常快速的。

select * from student where register_date > ‘2016-03-04‘;

  3.4 UPDATE 查询

  语法:

UPDATE table_name SET field1=new-value1, field2=new-value2
[WHERE Clause]

  更新数据:

mysql> update student set age=22 where stu_id = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

  3.5 DELETE 语句

  语法:

DELETE FROM table_name [WHERE Clause]

  删除语句:

mysql> delete from student where stu_id = 4;
Query OK, 1 row affected (0.00 sec)

  3.6 order by排序

  语法:

SELECT field1, field2,...fieldN table_name1, table_name2...
ORDER BY field1, [field2...] [ASC [DESC]]

  排序语句:

# 使用 ASC 或 DESC 关键字来设置查询结果是按升序或降序排列。 默认情况下,它是按升序排列。

mysql> select name, age, register_date from student order by age DESC;
+---------+-----+---------------+
| name    | age | register_date |
+---------+-----+---------------+
| lisi    |  31 | 2018-02-11    |
| bigberg |  22 | 2018-01-01    |
| zhansan |  21 | 2018-01-11    |
+---------+-----+---------------+
3 rows in set (0.00 sec)
mysql> select name, age, register_date from student order by age;
+---------+-----+---------------+
| name    | age | register_date |
+---------+-----+---------------+
| zhansan |  21 | 2018-01-11    |
| bigberg |  22 | 2018-01-10    |
| wangwu  |  22 | 2018-01-02    |
| lisi    |  31 | 2018-02-11    |
+---------+-----+---------------+
4 rows in set (0.00 sec)

mysql> select name, age, register_date from student order by age, register_date;
+---------+-----+---------------+
| name    | age | register_date |
+---------+-----+---------------+
| zhansan |  21 | 2018-01-11    |
| wangwu  |  22 | 2018-01-02    |
| bigberg |  22 | 2018-01-10    |
| lisi    |  31 | 2018-02-11    |
+---------+-----+---------------+
4 rows in set (0.00 sec)

  3.7 group by 分组

  语法:

SELECT column_name, function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;

  group by 语句

mysql> select age,count(*) as number from student group by age;
+-----+--------+
| age | number |
+-----+--------+
|  21 |      1 |
|  22 |      2 |
|  31 |      1 |
+-----+--------+
3 rows in set (0.00 sec)

  3.8 ALTER命令

  语法:

# 我们需要修改数据表名或者修改数据表字段时,就需要使用到MySQL ALTER命令
alter table student drop register_date; #从student表删除register_date   字段
alter table student add phone int(11) not null; #添加phone字段

  增加和删除字段

# 增加一个性别字段
mysql> alter table student add gender enum(‘M‘,‘F‘) NOT NULL;
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0


# 删除age字段
mysql> alter table student drop age;
Query OK, 0 rows affected (0.04 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select * from student;
+--------+---------+---------------+--------+
| stu_id | name    | register_date | gender |
+--------+---------+---------------+--------+
|      1 | bigberg | 2018-01-10    | M      |
|      2 | zhansan | 2018-01-11    | M      |
|      3 | lisi    | 2018-02-11    | M      |
|      5 | wangwu  | 2018-01-02    | M      |
|      6 | Lily    | 2018-02-23    | F      |
+--------+---------+---------------+--------+
5 rows in set (0.00 sec)

  修改字段类型

mysql> DESC student;
+---------------+---------------+------+-----+---------+----------------+
| Field         | Type          | Null | Key | Default | Extra          |
+---------------+---------------+------+-----+---------+----------------+
| stu_id        | int(11)       | NO   | PRI | NULL    | auto_increment |
| name          | char(32)      | NO   |     | NULL    |                |
| register_date | date          | NO   |     | NULL    |                |
| gender        | enum(‘M‘,‘F‘) | NO   |     | NULL    |                |
+---------------+---------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> alter table student modify name varchar(50);
Query OK, 5 rows affected (0.11 sec)
Records: 5  Duplicates: 0  Warnings: 0

mysql> desc student;
+---------------+---------------+------+-----+---------+----------------+
| Field         | Type          | Null | Key | Default | Extra          |
+---------------+---------------+------+-----+---------+----------------+
| stu_id        | int(11)       | NO   | PRI | NULL    | auto_increment |
| name          | varchar(50)   | YES  |     | NULL    |                |
| register_date | date          | NO   |     | NULL    |                |
| gender        | enum(‘M‘,‘F‘) | NO   |     | NULL    |                |
+---------------+---------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

  修改表名

mysql> alter table student rename to student_table;
Query OK, 0 rows affected (0.01 sec)

mysql> show tables;
+-----------------+
| Tables_in_study |
+-----------------+
| student_table   |
+-----------------+
1 row in set (0.00 sec)

  

 

Mysql 常用命令

标签:hone   where   cti   delete   偏移量   limit   size   phone   0.11   

原文地址:https://www.cnblogs.com/bigberg/p/8303380.html

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