title: ORA-00904 INVALID IDENTIFIER with Inner Join
body: <p>I'm trying to do an inner join between 3 tables in an ERD I created.  I've successfully built 3 - 3 layer sub-queries using these tables, and when I researched this issue, I can say that in my DDL, I didn't use double quotes so the columns aren't case sensitive.  Joins aren't my strong suite so any help would be much appreciated.  This is the query im putting in, and the error it's giving me.  All of the answers I've seen when people do inner joins they use the syntax, 'INNER JOIN' but I wasn't taught this? Is my method still okay?</p>
  
  <pre><code>SQL&gt; 
  SELECT  regional_lot.location, 
          rental_agreement.vin, 
          rental_agreement.contract_ID 
  FROM regional_lot, 
       rental_agreement 
  WHERE regional_lot.regional_lot_id = vehicle1.regional_lot_ID 
    AND vehicle1.vin = rental_agreement.vin;
  
  
                      *
  ERROR at line 1:
  ORA-00904: "VEHICLE1"."VIN": invalid identifier
  </code></pre>