How to drop a PostgreSQL database if there are active connections to it?

1、PostgreSQL 9.1 and below:

SELECT pg_terminate_backend(pg_stat_activity.procpid)
FROM pg_stat_activity
WHERE pg_stat_activity.datname = 'TARGET_DB'
  AND procpid <> pg_backend_pid();

PostgreSQL 9.2 and above:

SELECT pg_terminate_backend(pg_stat_activity.pid)
FROM pg_stat_activity
WHERE pg_stat_activity.datname = 'TARGET_DB'
  AND pid <> pg_backend_pid();

Once you disconnect everyone you will have to disconnect and issue the DROP DATABASE command from a connection from another database aka not the one your trying to drop.

Note the renaming of the procpid column to pid. See this mailing list thread.

pg_backend_pid:Process ID of the server process attached to the current session

2、

#!/usr/bin/env bash
# kill all connections to the postgres server
if [ -n "$1" ] ; then
  where="where pg_stat_activity.datname = '$1'"
  echo "killing all connections to database '$1'"
else
  echo "killing all connections to database"
fi

cat <<-EOF | psql -U postgres -d postgres 
SELECT pg_terminate_backend(pg_stat_activity.pid)
FROM pg_stat_activity
${where}
EOF

参考:

http://stackoverflow.com/questions/5408156/how-to-drop-a-postgresql-database-if-there-are-active-connections-to-it

http://www.postgresql.org/docs/9.3/static/functions-info.html