mysql练习

1：创建一个水费表单其中包括月份、用电率、费用

MariaDB [mysql]> create database shuifei;           #创建shuifei数据库
Query OK, 1 row affected (0.00 sec)

MariaDB [mysql]> use shuifei;                                #进入水费数据库      
Database changed

MariaDB [shuifei]> create table shuifei_info(月份 char(20) not null,用电率 char(50) not null,费用 char(30) not null,primary key(月份));                   #创建水费数据表
Query OK, 0 rows affected (0.01 sec)

MariaDB [shuifei]> show tables;                           #查看数据表
+-------------------+
| Tables_in_shuifei |
+-------------------+
| shuifei_info |
+-------------------+
1 row in set (0.00 sec)

MariaDB [shuifei]> desc shuifei_info;                  #查看水费表结构
+-----------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+----------+------+-----+---------+-------+
| 月份 | char(20) | NO | PRI | NULL | |
| 用电率 | char(50) | NO | | NULL | |
| 费用 | char(30) | NO | | NULL | |
+-----------+----------+------+-----+---------+-------+
3 rows in set (0.00 sec)

MariaDB [shuifei]> select * from shuifei_info;          #查看水费表内容
Empty set (0.00 sec)

MariaDB [shuifei]> insert into shuifei_info(月份,用电率,费用) values(‘十月份‘,289,144.5);      #插入数据
Query OK, 1 row affected (0.01 sec)

MariaDB [shuifei]> select * from shuifei_info;                 #查看水费表内容
+-----------+-----------+--------+
| 月份       | 用电率  | 费用 |
+-----------+-----------+--------+
| 十月份   | 289       | 144.5 |
+-----------+-----------+--------+
1 row in set (0.00 sec)

MariaDB [shuifei]> insert into shuifei_info values(‘九月份‘,289,144.5);             #插入九月份用电情况
Query OK, 1 row affected (0.00 sec)

MariaDB [shuifei]> select * from shuifei_info;                                                     
+-----------+-----------+--------+
| 月份 | 用电率 | 费用 |
+-----------+-----------+--------+
| 九月份    | 289       | 144.5 |
| 十月份    | 289       | 144.5 |
+-----------+-----------+--------+
2 rows in set (0.00 sec)

MariaDB [shuifei]> update shuifei_info set 用电率=300 where 月份=‘十月份‘;         #更新十月份用电情况
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

MariaDB [shuifei]> select * from shuifei_info;
+-----------+-----------+--------+
| 月份 | 用电率 | 费用 |
+-----------+-----------+--------+
| 九月份 | 289 | 144.5 |
| 十月份 | 300 | 144.5 |
+-----------+-----------+--------+
2 rows in set (0.00 sec)

2：创建一个学院名单包括姓名、年龄、总成绩

MariaDB [mysql]> create database 学员名单;
Query OK, 1 row affected (0.00 sec)

MariaDB [mysql]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| 学员名单 |
| auth |
| mydb |
| mysql |
| performance_schema |
| shuifei |
| test |
| yg |
+--------------------+
9 rows in set (0.00 sec)

MariaDB [mysql]> use 学员名单;
Database changed
MariaDB [学员名单]> show tables;
Empty set (0.00 sec)

MariaDB [学员名单]> create table mingdanbiao(姓名 char(10) not null,年龄 char(3) not null,总成绩 char(255) not null,primary key(姓名));
Query OK, 0 rows affected (0.00 sec)

MariaDB [学员名单]> desc mingdanbiao;
+-----------+-----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-----------+------+-----+---------+-------+
| 姓名 | char(10) | NO | PRI | NULL | |
| 年龄 | char(3) | NO | | NULL | |
| 总成绩 | char(255) | NO | | NULL | |
+-----------+-----------+------+-----+---------+-------+
3 rows in set (0.00 sec)

MariaDB [学员名单]> insert into mingdanbiao (姓名,年龄,总成绩)values(‘王亮‘,20,99);
Query OK, 1 row affected (0.00 sec)

MariaDB [学员名单]> select * from mingdanbiao;
+--------+--------+-----------+
| 姓名   | 年龄   | 总成绩  |
+--------+--------+-----------+
| 王亮   | 20      | 99         |
+--------+--------+-----------+
1 row in set (0.00 sec)

mysql练习

原文：https://www.cnblogs.com/CMX_Shmily/p/11671434.html