MariaDB [(none)]> use toyu
Database changed
MariaDB [toyu]> 
MariaDB [toyu]> 
MariaDB [toyu]> @stuId = ''
    -> ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '@stuId = ''' at line 1
MariaDB [toyu]> set @stuId = '';
Query OK, 0 rows affected (0.001 sec)

MariaDB [toyu]> SELECT stuId FROM student;
+--------+
| stuId  |
+--------+
| 100003 |
| 100007 |
| 100008 |
| 100000 |
| 100001 |
| 100002 |
| 100005 |
| 100006 |
| 100004 |
| 100009 |
| 100111 |
+--------+
11 rows in set (0.009 sec)

MariaDB [toyu]> SELECT stuId FROM student INTO @stuId;
ERROR 1172 (42000): Result consisted of more than one row
MariaDB [toyu]> SELECT GROUP_CONCAT(stuId) INTO @sutIDs FROM student;
Query OK, 1 row affected (0.005 sec)

MariaDB [toyu]> select @stuIDs;
+---------+
| @stuIDs |
+---------+
| NULL    |
+---------+
1 row in set (0.002 sec)

MariaDB [toyu]> SELECT GROUP_CONCAT(stuId) INTO @sutids FROM student;
Query OK, 1 row affected (0.001 sec)

MariaDB [toyu]> SELECT GROUP_CONCAT(stuId) INTO @stuids FROM student;
Query OK, 1 row affected (0.000 sec)

MariaDB [toyu]> SELECT @stuIds;
+------------------------------------------------------------------------------+
| @stuIds                                                                      |
+------------------------------------------------------------------------------+
| 100003,100007,100008,100000,100001,100002,100005,100006,100004,100009,100111 |
+------------------------------------------------------------------------------+
1 row in set (0.001 sec)

MariaDB [toyu]> show databases;
+--------------------+
| Database           |
+--------------------+
| ctetinker          |
| dbtool             |
| ds                 |
| information_schema |
| mysql              |
| performance_schema |
| phpmyadmin         |
| swim               |
| toyu               |
+--------------------+
9 rows in set (0.002 sec)

MariaDB [toyu]> SELECT DISTINCT u.user, u.password
    -> FROM mysql.user AS u
    -> WHERE u.host = 'localhost'; 
+-------+-------------------------------------------+
| User  | Password                                  |
+-------+-------------------------------------------+
| d5333 | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| demo  | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| pma   |                                           |
| root  |                                           |
| s1    | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| s2    | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| yue   | *0BE23F42F79ABCFD46E7AF357A07122B6C495EA8 |
+-------+-------------------------------------------+
7 rows in set (0.025 sec)

MariaDB [toyu]> 
MariaDB [toyu]> SELECT DISTINCT u.host, u.user, u.password
    -> FROM mysql.user AS u;
+-----------+-------+-------------------------------------------+
| Host      | User  | Password                                  |
+-----------+-------+-------------------------------------------+
| localhost | root  |                                           |
| %         | yue   | *0BE23F42F79ABCFD46E7AF357A07122B6C495EA8 |
| 127.0.0.1 | root  |                                           |
| ::1       | root  |                                           |
| localhost | pma   |                                           |
| localhost | yue   | *0BE23F42F79ABCFD46E7AF357A07122B6C495EA8 |
| %         | demo  | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| localhost | demo  | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| %         | s1    | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| localhost | s1    | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| %         | s2    | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| localhost | s2    | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| %         | d5333 | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
| localhost | d5333 | *C2D24DCA38E9E862098B85BF0AB35CAA52803797 |
+-----------+-------+-------------------------------------------+
14 rows in set (0.003 sec)

MariaDB [toyu]> SELECT table_name, table_type, row_format, table_rows, avg_row_length
    -> FROM information_schema.tables
    -> WHERE table_schema = 'toyu'
    -> ORDER BY table_name DESC;
+----------------+------------+------------+------------+----------------+
| table_name     | table_type | row_format | table_rows | avg_row_length |
+----------------+------------+------------+------------+----------------+
| student        | BASE TABLE | Dynamic    |         11 |           1489 |
| school_summary | VIEW       | NULL       |       NULL |           NULL |
| school         | BASE TABLE | Dynamic    |          4 |           4096 |
| grade          | BASE TABLE | Dynamic    |         15 |           1092 |
| faculty        | BASE TABLE | Dynamic    |         11 |           1489 |
| enroll         | BASE TABLE | Dynamic    |         22 |            744 |
| department     | BASE TABLE | Dynamic    |          7 |           2340 |
| course         | BASE TABLE | Dynamic    |         11 |           1489 |
| class          | BASE TABLE | Dynamic    |         14 |           1170 |
+----------------+------------+------------+------------+----------------+
9 rows in set (0.002 sec)

MariaDB [toyu]> SELECT table_name, table_type, row_format, table_rows, avg_row_length
    -> FROM information_schema.tables
    -> WHERE table_schema = 'toyu'
    -> AND table_type = 'BASE TYPE'
    -> ORDER BY table_name DESC;
Empty set (0.002 sec)

MariaDB [toyu]> SELECT table_name, table_type, row_format, table_rows, avg_row_length
    -> FROM information_schema.tables
    -> WHERE table_schema = 'toyu'
    -> AND table_type = 'BASE TABLE'
    -> ORDER BY table_name DESC;
+------------+------------+------------+------------+----------------+
| table_name | table_type | row_format | table_rows | avg_row_length |
+------------+------------+------------+------------+----------------+
| student    | BASE TABLE | Dynamic    |         11 |           1489 |
| school     | BASE TABLE | Dynamic    |          4 |           4096 |
| grade      | BASE TABLE | Dynamic    |         15 |           1092 |
| faculty    | BASE TABLE | Dynamic    |         11 |           1489 |
| enroll     | BASE TABLE | Dynamic    |         22 |            744 |
| department | BASE TABLE | Dynamic    |          7 |           2340 |
| course     | BASE TABLE | Dynamic    |         11 |           1489 |
| class      | BASE TABLE | Dynamic    |         14 |           1170 |
+------------+------------+------------+------------+----------------+
8 rows in set (0.002 sec)

MariaDB [toyu]> ;
ERROR: No query specified

MariaDB [toyu]> SELECT table_name, table_type, row_format, table_rows, avg_row_length, create_time
    -> FROM information_schema.tables
    -> WHERE table_schema = 'toyu'
    -> AND table_type = 'BASE TABLE'
    -> ORDER BY table_name DESC;
+------------+------------+------------+------------+----------------+---------------------+
| table_name | table_type | row_format | table_rows | avg_row_length | create_time         |
+------------+------------+------------+------------+----------------+---------------------+
| student    | BASE TABLE | Dynamic    |         11 |           1489 | 2024-09-25 17:17:41 |
| school     | BASE TABLE | Dynamic    |          4 |           4096 | 2024-09-25 17:17:41 |
| grade      | BASE TABLE | Dynamic    |         15 |           1092 | 2024-09-25 17:17:41 |
| faculty    | BASE TABLE | Dynamic    |         11 |           1489 | 2024-09-25 17:17:41 |
| enroll     | BASE TABLE | Dynamic    |         22 |            744 | 2024-09-25 17:17:41 |
| department | BASE TABLE | Dynamic    |          7 |           2340 | 2024-09-25 17:17:41 |
| course     | BASE TABLE | Dynamic    |         11 |           1489 | 2024-09-25 17:17:41 |
| class      | BASE TABLE | Dynamic    |         14 |           1170 | 2024-09-25 17:17:41 |
+------------+------------+------------+------------+----------------+---------------------+
8 rows in set (0.003 sec)

MariaDB [toyu]> -- databases and tables
MariaDB [toyu]> SELECT t.TABLE_SCHEMA AS `schema`, COUNT(t.TABLE_NAME) AS num_tables
    -> FROM information_schema.tables AS t
    -> GROUP BY `schema`
    -> ORDER BY num_tables DESC;
+--------------------+------------+
| schema             | num_tables |
+--------------------+------------+
| information_schema |         79 |
| performance_schema |         52 |
| mysql              |         31 |
| phpmyadmin         |         19 |
| swim               |         13 |
| toyu               |          9 |
| ds                 |          1 |
+--------------------+------------+
7 rows in set (0.003 sec)

MariaDB [toyu]> SELECT t.TABLE_SCHEMA AS `schema`, t.ENGINE, COUNT(t.TABLE_NAME) AS num_tables
    -> FROM information_schema.tables t
    -> GROUP BY `schema`, t.ENGINE
    -> ORDER BY `schema`, num_tables DESC;
+--------------------+--------------------+------------+
| schema             | ENGINE             | num_tables |
+--------------------+--------------------+------------+
| ds                 | InnoDB             |          1 |
| information_schema | MEMORY             |         66 |
| information_schema | Aria               |         13 |
| mysql              | Aria               |         24 |
| mysql              | InnoDB             |          4 |
| mysql              | CSV                |          2 |
| mysql              | NULL               |          1 |
| performance_schema | PERFORMANCE_SCHEMA |         52 |
| phpmyadmin         | InnoDB             |         19 |
| swim               | InnoDB             |         13 |
| toyu               | InnoDB             |          8 |
| toyu               | NULL               |          1 |
+--------------------+--------------------+------------+
12 rows in set (0.123 sec)

MariaDB [toyu]> CALL count_columns('toyu', 'student', @column_count);
ERROR 1305 (42000): PROCEDURE toyu.count_columns does not exist
MariaDB [toyu]> SELECT @column_count;
+---------------+
| @column_count |
+---------------+
| NULL          |
+---------------+
1 row in set (0.000 sec)

MariaDB [toyu]> CALL count_columns('swim', 'swimmer', @column_count);
ERROR 1305 (42000): PROCEDURE toyu.count_columns does not exist
MariaDB [toyu]> SELECT @column_count;
+---------------+
| @column_count |
+---------------+
| NULL          |
+---------------+
1 row in set (0.000 sec)

MariaDB [toyu]> USE dbtool;
Database changed
MariaDB [dbtool]> CALL count_columns('toyu', 'student', @column_count);
Query OK, 1 row affected (0.015 sec)

MariaDB [dbtool]> SELECT @column_count;
+---------------+
| @column_count |
+---------------+
|             7 |
+---------------+
1 row in set (0.000 sec)

MariaDB [dbtool]> CALL count_columns('swim', 'swimmer', @column_count);
Query OK, 1 row affected (0.011 sec)

MariaDB [dbtool]> SELECT @column_count;
+---------------+
| @column_count |
+---------------+
|            10 |
+---------------+
1 row in set (0.000 sec)

MariaDB [dbtool]> notee