mysql> show status like 'Threads%';
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| Threads_cached | 58 |
| Threads_connected | 57 | ###这个数值指的是打开的连接数
| Threads_created | 3676 |
| Threads_running | 4 | ###这个数值指的是激活的连接数，这个数值一般远低于connected数值
+-------------------+-------+
Threads_connected 跟show processlist结果相同，表示当前连接数。准确的来说，Threads_running是代表当前并发数
这是是查询数据库当前设置的最大连接数
mysql> show variables like '%max_connections%';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 1000 |
+-----------------+-------+