创建数据库：Navicat软件中，mysql80右击选中命令列介面，输入CREATE DATABASE itcast; 然后回车输入SHOW DATABASES; 然后回车，输入SHOW CREATE DATABASE itcast;
删除数据库：输入DROP DATABASE itcast; （删除itcast），回车，然后可以查看一下是否删除，输入SHOW DATABASES;
以下是成功的命令
mysql> DROP DATABASE itcast;
Query OK, 0 rows affected
mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set
mysql> CREATE TABLE tb_grade
-> (
-> id INT(11),
-> name VARCHAR(20),
-> grade FLOAT
-> );
Query OK, 0 rows affected
mysql> SHOW TABLES;
+------------------+
| Tables_in_itcast |
+------------------+
| tb_grade |
+------------------+
1 row in set
mysql> CREATE TABLE tb_grade
-> (
-> id INT(11),
-> name VARCHAR(20),
-> grade FLOAT
-> );
Query OK, 0 rows affected
mysql> SHOW TABLES;
+------------------+
| Tables_in_itcast |
+------------------+
| tb_grade |
+------------------+
1 row in set