Often in development environment you want to truncate all the tables to insert new data from production, but you cannot do easily as there were a bumch of Foreign Keys and triggers. Dropping all triggers and FK's and then recreating them again is a tedious job. That to dropping and recreating FK's in a particular order. Here is a simple script to disable and enable all your constraints and trigger.
I go this script from one of my friend in sql forums. Posting here, so that it could be helpful to user commnity.
When doing bulk data changes it may be beneficial to disable indexes prior to starting the operation. Fortunately, SQL's rich metadata makes this very easy to automate in a robust fashion.