title: Is Observer pattern and pub-sub same when a database is used in the implementation?
body: <p>I am trying to understand observer pattern and stuck at one particular point. In my understanding, once an observer subscribes to notify them on any event change, the subscription is stored somewhere and then when event changes the subscriber is notified.</p>
  
  <p>In practical scenarios I should store the values in a database or a file for persistence  reasons and inform them once event occurs by getting from db and looping through the list.</p>
  
  <p>Is this correct understanding? I do not see any example involving database but, every example uses list.</p>
  
  <p>And again publisher/subscriber pattern is also similar except with the change that there is no exact knowledge of who the publisher and subscribers are and intermediate technologies like MQ or some sort is used to establish communication between two.</p>
  
  <p>My question is : When we use DB in observer pattern wont it become publisher/subscriber ( except there is knowledge of observers and publishers here). Is it correct understanding?</p>