use public;

Affected Rows: 0

select database();

+------------+
| database() |
+------------+
| public     |
+------------+

select schema();

+----------+
| schema() |
+----------+
| public   |
+----------+

select user(), current_user(), system_user();

+----------+----------------+---------------+
| user()   | current_user() | system_user() |
+----------+----------------+---------------+
| greptime | greptime       | greptime      |
+----------+----------------+---------------+

use information_schema;

Affected Rows: 0

select database();

+--------------------+
| database()         |
+--------------------+
| information_schema |
+--------------------+

select schema();

+--------------------+
| schema()           |
+--------------------+
| information_schema |
+--------------------+

use public;

Affected Rows: 0