说明

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| test               |
+--------------------+
5 rows in set (0.02 sec)

数据库存在
删除报错

mysql> drop database test;
ERROR 1008 (HY000): Can't drop database 'test'; database doesn't exist

解决方案

drop database if exists test;