First, find the activities that are taken place against the target
database, you can query thepg_stat_activity view
as the following query:
SELECT * FROM pg_stat_activity WHERE datname = ‘target_database‘;
Second, terminate the active connections by issuing the following query:
SELECT pg_terminate_backend (pg_stat_activity.pid) FROM pg_stat_activity WHERE pg_stat_activity.datname = ‘target_database‘;
Notice that if you use PostgreSQL version 9.1 or earlier, use the procpid column instead of the pid column because PostgreSQL changed procid column to pid column since version 9.2
Third, execute the DROP
DATABASE statement:
DROP DATABASE target_database;
postgreSQLG关闭活动的connection、删除活动的数据库
原文：http://www.cnblogs.com/paulbai/p/3533920.html