接続セッション一覧 : show processlist;

mysql> show processlist;
+-------+-----------------+-----------------+----------+---------+------+-----------------------------+------------------+
| Id    | User            | Host            | db       | Command | Time | State                       | Info             |
+-------+-----------------+-----------------+----------+---------+------+-----------------------------+------------------+
|     1 | event_scheduler | localhost       | NULL     | Daemon  |    9 | Waiting for next activation | NULL             |
| 67692 | root            | localhost       | ?????    | Query   |    0 | starting                    | show processlist |
| 68108 | root            | 127.0.0.1:43480 | ?????    | Sleep   |   21 |                             | NULL             |
| 68224 | root            | 127.0.0.1:43712 | ???????? | Sleep   |   29 |                             | NULL             |
| 68408 | root            | 127.0.0.1:45742 | ???????? | Sleep   |   24 |                             | NULL             |
+-------+-----------------+-----------------+----------+---------+------+-----------------------------+------------------+
5 rows in set (0.00 sec)

接続セッション数 : show status like ‘Threads_connected’; または SELECT COUNT(*) FROM information_schema.PROCESSLIST;

mysql> show status like 'Threads_connected';
+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| Threads_connected | 4     |
+-------------------+-------+
1 row in set (0.01 sec)

mysql> SELECT count(*) FROM information_schema.PROCESSLIST;
+----------+
| count(*) |
+----------+
|        5 |
+----------+
1 row in set (0.00 sec)

最大接続設定 : show global variables like ‘max_connections’;

mysql> show global variables like 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | ???   |
+-----------------+-------+
1 row in set (0.00 sec)