What treatment does so-called "Dental emergency pain-relief procedure" involves?

When dental pain becomes unbearable one may seek immediate help from dentist, and this is when "emergency pain-relief procedure" is implemented. But I wonder what dentists usually do to relieve pain (in my case, the pain is caused by a decayed teeth which is in very bad shape and a root and c is a must)? My guess is that dentists will give freezings and prescribe codeine pain relievers that are good 'til the day of the appointment.