基础MySQL 增删改查 + 删库

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本文详细介绍MySQL数据库的基本操作，包括创建数据库、数据表，插入、更新、删除数据，以及最终删除数据库的全过程。通过实例演示了如何使用SQL语句进行数据库管理。

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mysql> SHOW DATABASES;                  查看数据库信息，默认是4个库，
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.00 sec)

mysql> CREATE DATABASE Feiyu;            创建Feiyu数据库，
Query OK, 1 row affected (0.00 sec)
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| feiyu              |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)
mysql> USE Feiyu;                        直接打开Feiyu数据库，
Database changed
mysql>

mysql> CREATE TABLE one(                 创建one数据列表，
    -> username VARCHAR (20),
    -> age TINYINT UNSIGNED,
    -> salary FLOAT (8,2) UNSIGNED
    -> );
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW TABLES;
+-----------------+
| Tables_in_feiyu |
+-----------------+
| one             |
+-----------------+
1 row in set (0.00 sec)

mysql> SHOW columns from one;           one列表中的字段，
+----------+---------------------+------+-----+---------+-------+
| Field    | Type                | Null | Key | Default | Extra |
+----------+---------------------+------+-----+---------+-------+
| username | varchar(20)         | YES  |     | NULL    |       |
| age      | tinyint(3) unsigned | YES  |     | NULL    |       |
| salary   | float(8,2) unsigned | YES  |     | NULL    |       |
+----------+---------------------+------+-----+---------+-------+
3 rows in set (0.03 sec)

mysql> INSERT INTO one                  添加，
    -> (username,age,salary)
    -> values
    -> ("one","1","1000");
Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM one;
+----------+------+---------+
| username | age  | salary  |
+----------+------+---------+
| one      |    1 | 1000.00 |
+----------+------+---------+
1 row in set (0.00 sec)
                                        修改，                                              
mysql> update one set username="two" where username="one";  
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

                                        删除数据列表，
mysql> delete from one where username="two";
Query OK, 1 row affected (0.00 sec)

                                        删除刚刚创建Feiyu数据库，
mysql> drop DATABASE Feiyu;
Query OK, 1 row affected (0.01 sec)
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.00 sec)                现在回到没有创建之前情形；