How to Remove a Duplicate CaseID Programatically in Salesforce?

Hi,

You can use trigger to delete the duplicate ids as follows:-

Trigger deleteduplicate on Student__c (before insert)
{
set<String> uniqueIds = new set<Id>();

for (Student__c s : Trigger.new)
uniqueIds.add(s.StudentId__c);

list<Student__c> existingstudents = [select StudentId__c from Student__c where StudentId__c in :uniqueIds];

list<Student__c> dupestodelete = new list<Student__c>();
for (Student__c s : Trigger.new)
{
for (Student__c existing : existingstudents)
{
if (s.StudentId__c == existing.StudentId__c)
{
dupestodelete.add(s);
continue;
}
}
}

delete dupestodelete;

}