每个MySQL连接，都有一个连接ID，可以通过 connection_id()查看。
连接id也可以通过以下方式查看：
show processlist中id列information_schema.processlist的id列performance_schema.threads的processlist_id 列下面通过具体命令查看连接id。
查看连接id:
mysql> select connection_id(); +-----------------+ | connection_id() | +-----------------+ | 15 | +-----------------+ 1 row in set (0.00 sec)查看show processlist:
mysql> show processlist; +----+------+-----------------+------+---------+------+----------+------------------+ | Id | User | Host | db | Command | Time | State | Info | +----+------+-----------------+------+---------+------+----------+------------------+ | 3 | root | localhost:60989 | cmdb | Sleep | 318 | | NULL | | 4 | root | localhost:60990 | cmdb | Sleep | 318 | | NULL | | 15 | root | localhost | NULL | Query | 0 | starting | show processlist | +----+------+-----------------+------+---------+------+----------+------------------+ 3 rows in set (0.00 sec)查看数据表information_schema.processlist:
mysql> select * from information_schema.processlist; +----+------+-----------------+------+---------+------+-----------+-----------------------------------------------+ | ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO | +----+------+-----------------+------+---------+------+-----------+-----------------------------------------------+ | 3 | root | localhost:60989 | cmdb | Sleep | 157 | | NULL | | 15 | root | localhost | NULL | Query | 0 | executing | select * from INFORMATION_SCHEMA.PROCESSLIST | | 4 | root | localhost:60990 | cmdb | Sleep | 157 | | NULL | +----+------+-----------------+------+---------+------+-----------+-----------------------------------------------+ 3 rows in set (0.00 sec)查看数据表performance_schema.threads：
mysql> select thread_id, name, processlist_id from performance_schema.threads; +-----------+----------------------------------------+----------------+ | thread_id | name | processlist_id | +-----------+----------------------------------------+----------------+ | 1 | thread/sql/main | NULL | | 2 | thread/sql/thread_timer_notifier | NULL | | 3 | thread/innodb/io_ibuf_thread | NULL | | 4 | thread/innodb/io_log_thread | NULL | | 5 | thread/innodb/io_read_thread | NULL | | 6 | thread/innodb/io_read_thread | NULL | | 7 | thread/innodb/io_read_thread | NULL | | 8 | thread/innodb/io_read_thread | NULL | | 9 | thread/innodb/io_write_thread | NULL | | 10 | thread/innodb/io_write_thread | NULL | | 11 | thread/innodb/io_write_thread | NULL | | 12 | thread/innodb/io_write_thread | NULL | | 13 | thread/innodb/page_cleaner_thread | NULL | | 16 | thread/innodb/srv_lock_timeout_thread | NULL | | 15 | thread/innodb/srv_error_monitor_thread | NULL | | 17 | thread/innodb/srv_monitor_thread | NULL | | 18 | thread/innodb/srv_master_thread | NULL | | 19 | thread/innodb/srv_worker_thread | NULL | | 20 | thread/innodb/srv_worker_thread | NULL | | 21 | thread/innodb/srv_purge_thread | NULL | | 22 | thread/innodb/srv_worker_thread | NULL | | 23 | thread/innodb/buf_dump_thread | NULL | | 24 | thread/innodb/dict_stats_thread | NULL | | 25 | thread/sql/signal_handler | NULL | | 26 | thread/sql/compress_gtid_table | 1 | | 28 | thread/sql/one_connection | 3 | | 29 | thread/sql/one_connection | 4 | | 40 | thread/sql/one_connection | 15 | +-----------+----------------------------------------+----------------+ 28 rows in set (0.00 sec)https://dev.mysql.com/doc/refman/5.7/en/information-functions.html
https://dev.mysql.com/doc/refman/5.7/en/threads-table.html
