Trigger to avoid duplicate value

This is my first Post and I hope it will help you all.

You can use Trigger to avoid duplicate value.In the below example I am avoiding duplicate value for job name in the system.

trigger AvoidDuplicateJobName on Job__c(before insert, before update) 
{
 Set<String> setJobName = new Set<String>();

 for (Job__c job : [SELECT Name FROM Job__c WHERE Id Not IN: Trigger.new])
 {   
  setJobName.add(job.Name);
 }

 for (Job__c job : System.Trigger.new) 
 {
  if (setJobName.contains(job.Name)) 
  {
   job.Name.addError('Another new Job has the '+ 'same Name.');
  }
  else if(!setJobName.contains(job.Name))
  {
   setJobName.add(job.Name);
  }
 }
}