问题：
Is there a command in PostgreSQL to select active connections to a given database? PostgreSQL 中是否有一个命令可以选择到给定数据库的活动连接？
psql states that I can't drop one of my databases because there are active connections to it , so I would like to see what the connections are (and from which machines) psql声明我不能删除我的数据库之一，因为有活动连接到它，所以我想看看连接是什么（以及来自哪些机器）
解决方案：
参考一： https://stackoom.com/question/1r7JX参考二： How to list active connections on PostgreSQL?