title: What happens to autoincrement primary keys after delete?
body: <p>I'm trying to create a database file with objects and sub-objects. For example, </p>
  
  <p>The first table would be of jars for storing change. Each jar entry would have a autoincrement primary ID key and data about the jar, like height, diameter or whatever.</p>
  
  <p>The second table would contain the coins. Each coin would have an ID (needed?) and would also have the ID of the jar that it is contained in and it's data (like value, year, etc.).</p>
  
  <p>My question is what happens to the autoincrement keys when one is deleted? Say you had 4 jars:</p>
  
  <p>1
  2
  3
  4</p>
  
  <p>and you deleted number 2. Would the remaining jars be renumbered 123? or would there be a gap? If there is a gap, is it filled so the next jar created would have an ID of 2? or would the next one still be 5?</p>
  
  <p>Thanks</p>