Apex Trigger Events|Apex Trigger Exaples

Trigger Examples:
What is Trigger? Trigger is piece of code that is executes before and after a record is Inserted/Updated/Deleted from the force.com database.
Trigger Events: Before Insert, Before Update, Before Delete, After Insert, After Update, After Delete and after undelete.
Example 1:

trigger trigEventsTest on Department__c (before insert,after insert,before update,after update) {
	if(Trigger.isInsert) {
		system.debug('***IsINSERT*****');
	}

	if(Trigger.isUpdate) {
		system.debug('******IsUpdate*****');
	}

	if(Trigger.isBefore && Trigger.isInsert) {
		system.debug('****IsBefore and IsInsert*****');
	}

	if(Trigger.isAfter && Trigger.isInsert) {
		system.debug('*******IsAfter and IsInsert*****');
	}

	if(Trigger.isBefore && Trigger.isUpdate) {
		system.debug('*****Before Update******');
	}
}

Example 2:
Account with Multiple Contacts:

trigger Con5Insert on Account (after insert) {
	if(Trigger.isAfter) {
		system.debug('****New Account Record is ******'+Trigger.new);
		Contact objContact ;
		List<Contact> lstcon = new List<Contact>();
		for(Integer i=1;i<=5;i++) {
			objContact = new Contact(lastname='AAAAAAAAA'+string.valueof(i),AccountId=Trigger.new[0].Id);
			lstcon.add(objContact);
		}
		system.debug('****List Of Contacts *****'+lstcon.size());
		insert lstCon;
	}
}

Example 3:
Trigger.new and Trigger.old

trigger trigEventsTest on Department__c (before update,after update) {
	if (Trigger.new[0].name != Trigger.new[0].name) {
		system.debug('*****Value Changed******');
	} else {
		system.debug('*****Value did not change******');
	}
}

Example 4:
Add Error:

trigger trigEventsTest on Department__c (before insert) {
	if(Trigger.new[0].name=='India') {
		Trigger.new[0].name.addError('Name should not be India');
	}
}