一、查库
##1）库:一个库就是一个excell文档，库里含有表,一个表就是一个excell的sheet.
##2）查看数据库实例中有哪些库
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema | #系统运行状态，性能等的库。
| mysql | #授权权限、用户管理的库
| performance_schema | #系统运行状态，性能等的库。
| test | #临时库
##3）查看有含有te字符串的库
MariaDB [mysql]> show databases like '%te%';
+-----------------+
| Database (%te%) |
+-----------------+
| test |
+-----------------+
1 row in set (0.00 sec)
use test;
#方法1：直接看提示符MariaDB [test]>
#方法2：select database();二、删库
##库名用小写，命令不分大小写，推荐小写。
drop database test;三、建库
##默认建库
create database oldboy;
show databases;
四、查看建库SQL语句
MariaDB [mysql]> show create database oldboy;
+----------+--------------------------------------------------------------------+
| Database | Create Database |
+----------+--------------------------------------------------------------------+
| oldboy | CREATE DATABASE `oldboy` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+--------------------------------------------------------------------+
说明：可以看到库的字符集已经被默认指定latin1。+ -------------------- +
## 字符集介绍：简单说就是一个 [ 密码本 ] ：
企业工作字符集 :
utf8,gbk, 当下最主流就是 utf8mb4 （ 8.0 默认的字符集）
## 指定字符集建库：
语法：
CREATE DATABASE 数据库名字
CHARACTER SET 字符集
COLLATE 校队规则 ;
## 高版本数据库，直接 CREATE DATABASE 数据库名字 ; 即可。
五、 改库
##修改oldboy数据库字符集为utf8mb4：
alter database oldboy character set utf8mb4;
show create database oldboy;
#查看数据库字符集
MariaDB [(none)]> show charset;
+----------+-----------------------------+---------------------+--------+
| 字符集 | 描述 |校对规则 | Maxlen |
+----------+-----------------------------+---------------------+--------+
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 | ##推荐
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 | ##新的
+----------+-----------------------------+---------------------+--------+
39 rows in set (0.00 sec)
##查看建库语句
MariaDB [(none)]> show create database oldgirl;
+----------+------------------------------------------------------------------
##指定字符集建oldgirl库（注意字符集和校对规则查上表）
MariaDB [(none)]> create database oldgirl character set utf8 collate
utf8_general_ci;
Query OK, 1 row affected (0.00 sec)
+
| Database | Create Database |
+----------+------------------------------------------------------------------+
| oldgirl | CREATE DATABASE `oldgirl` /*!40100 DEFAULT CHARACTER SET utf8 */
|##utf8
+----------+------------------------------------------------------------------+
1 row in set (0.00 sec)
##再查看oldboy建库语句
MariaDB [(none)]> show create database oldboy;
+----------+-----------------------------------------------------------------+
| Database | Create Database |
+----------+-----------------------------------------------------------------+
| oldboy | CREATE DATABASE `oldboy` /*!40100 DEFAULT CHARACTER SET utf8 */ |#已
##将oldboy库的字符集改为utf8
MariaDB [(none)]> alter database oldboy character set utf8;
Query OK, 1 row affected (0.00 sec
##查看oldboy建库语句
MariaDB [(none)]> show create database oldboy;
+----------+-------------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------------+
| oldboy | CREATE DATABASE
`oldboy` /*!40100 DEFAULT CHARACTER SET latin1 */
|##latin1
+----------+-------------------------------------------------------------------+
1 row in set
(0.00 sec)
)
改+----------+-----------------------------------------------------------------+
1 row in set (0.00 sec)
