title: MySQL Combine Two Very Large Tables when three columns are equal
body: <p>I have two very large tables, Table1 and Table2.  They look like this:</p>
  
  <p>Table1 (800k records): Name, BirthDate, OrderNumber, col4, col5, col6.</p>
  
  <p>Table2 (200k records): Name, BirthDate, OrderNumber, col4, col5, col6.</p>
  
  <p>How can I select all records from table 1 which don't have a matching Name, BirthDate, OrderNumber combination in table 2?  The rest of the columns don't matter.</p>
  
  <p>I've tried doing this query below which runs for at least a couple minutes with no apparent end.  Right now I am just trying to select the records then i can figure out how to combine the tables.</p>
  
  <pre><code>Select Table1.Name, Table1.BirthDate, Table1.OrderNumber from Table1
  left join Table2 ON 
  Table1.Name=Table2.Name AND
  Table1.BirthDate=Table2.BirthDate AND
  Table1.OrderNumber=Table2.OrderNumber AND 
  WHERE Table2.Name IS NULL;
  </code></pre>