SQL语句
SQL语句分类:
DDL 数据定义语言
DCL 数据控制语言
DML 数据操作语言
- DDL:(Data Defined Language)
- create
- alter
- drop
- DML:(Data Manapulating Language)
- insert
- delete
- update
- select
- DCL: (Data Control Language)
- grant
- revoke
1、DDL 数据定义语言:
1.1库
1.1.1增(create)
建库的时候要注意修改库的字符集,使用charset 命令
这里注意utfmb4相较于utf8多了emoji 表情的字符类型
mysql> create database word charset utf8mb4;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| word |
| world |
+--------------------+
7 rows in set (0.00 sec)
mysql>
1.1.2删库(drop)
mysql> drop database word ;
Query OK, 0 rows affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| world |
+--------------------+
6 rows in set (0.00 sec)
mysql>
1.1.3查看库(show)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| word |
| world |
+--------------------+
7 rows in set (0.00 sec)
mysql> show create database word
-> ;
+----------+------------------------------------------------------------------+
| Database | Create Database |
+----------+------------------------------------------------------------------+
| word | CREATE DATABASE `word` /*!40100 DEFAULT CHARACTER SET utf8mb4 */ |
+----------+------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
1.1.4修改库(alter)
mysql> create database word;
Query OK, 1 row affected (0.00 sec)
mysql> show create database word;
+----------+-----------------------------------------------------------------+
| Database | Create Database |
+----------+-----------------------------------------------------------------+
| word | CREATE DATABASE `word` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> alter database word charset utf8mb4;
Query OK, 1 row affected (0.00 sec)
mysql> show create database word;
+----------+------------------------------------------------------------------+
| Database | Create Database |
+----------+------------------------------------------------------------------+
| word | CREATE DATABASE `word` /*!40100 DEFAULT CHARACTER SET utf8mb4 */ |