example in postgresql old version:

-- login psql
-- makesure db exist
-- Disallow new connections
UPDATE pg_database SET datallowconn = false WHERE datname = "NAMA_DB";
-- ALTER DATABASE "NAMA_DB" CONNECTION LIMIT 1; -- (jika perlu)

-- teriminate existing connection
SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname = "NAMA_DB";

-- delete
DROP DATABASE "NAMA_DB";

Ref https://dba.stackexchange.com/questions/11893/force-drop-db-while-others-may-be-connected