How to delete child records in lookup relation (with Salesforce triggers)

Check out this one.. Click here to get the solution DeleteChildrenFromOppty

You can optimize it further based on design patterns you use.

trigger deleteuniversity on University__c (before insert,before delete,after delete) {
set<id> ids =new set<id>();
if(trigger.isbefore && trigger.isdelete)
{
for(University__c u:trigger.old)
{
ids.add(u.id);
}
system.debug('ma size'+ids);
Deleteuniversityhelper.emp =[SELECT Id, University__c FROM Employeee__c where University__c in:ids];
}
if(trigger.isafter && trigger.isdelete)
{ system.debug('ma size'+Deleteuniversityhelper.emp);
delete Deleteuniversityhelper.emp;
}

}

public class Deleteuniversityhelper {
public static list<Employeee__c> emp;
}