title: "Core Data is not a relational database." Why exactly is this important to know?
body: <p>I realize this may be common sense for a lot of people, so apologies if this seems like a stupid question.</p>
  
  <p>I am trying to learn core data for iOS programming, and I have repeatedly read and heard it said that Core Data (CD) is not a relational database.  But very little else is said about this, or why exactly it is important to know beyond an academic sense.  I mean functionally at least, it seems you can use CD as though it were a database for most things - storing and fetching data, runnings queries etc.  From my very rudimentary understanding of it, I don't really see how it differs from a database.</p>
  
  <p>I am not questioning the fact that the distinction is important.  I believe that a lot of smart people would not be wasting their time on this point if it weren't useful to understand.  But I would like someone please to explain - ideally with examples - how CD not being a relational database affects how we use it?  Or perhaps, if I were not told that CD isn't a relational database, how would this adversely impact my performance as an Objective-C/Swift programmer?</p>
  
  <p>Are there things that one might try to do incorrectly if they treated CD as a relational database?  Or, are there things which a relational database cannot do or does less well that CD is designed to do?</p>
  
  <p>Thank you all for your collective wisdom. </p>