title: More efficient to have two tables or one table with tons of fields
body: <p>Related but not quite the same thing:<a href="https://stackoverflow.com/questions/1125004/which-is-more-efficient-multiple-mysql-tables-or-one-large-table">which is more effcient?</a> (or at least reading through it didn't help me any)</p>
  
  <p>So I am working on a new site (selling insurance policies) we already have several sites up (its a rails application) that do this so I have a table in my sql database called policies.
  As you can imagine it has lots of columns to support all the different options available.</p>
  
  <p>While working on this new site I realized I needed to keep track of 20+ more options. </p>
  
  <p>My concern is that the policies table is already large, but the columns in it right now are almost all used by every application we have. Whereas if I add these they would only be used for the new site and would leave tons of null cells on all the rest of the policies.</p>
  
  <p>So my question is do I add those to the existing table or create a new table just for the policies sold on that site? Also I believe that if I created a new table I could leave out some of the columns (but not very many) from the main policies table because they are not needed for this application.  </p>