title: Why use a 1-to-1 relationship in database design?
body: <p>I am having a hard time trying to figure out when to use a 1-to-1 relationship in db design or if it is ever necessary.</p>
  
  <p>If you can select only the columns you need in a query is there ever a point to break up a table into 1-to-1 relationships. I guess updating a large table has more impact on performance than a smaller table and I'm sure it depends on how heavily the table is used for certain operations (read/ writes)</p>
  
  <p>So when designing a database schema how do you factor in 1-to-1 relationships? What criteria do you use to determine if you need one, and what are the benefits over not using one?</p>