title: What is the purpose of a DataRelation in a DataSet?
body: <p>A C# program I am working on will need to export data to one or more tables of data. Some columns of these tables will be related to one another, such that the ID column of of one table may be reference by the cell of another table. This seems like the common case for setting up a DataRelation. But I'm trying to understand how these relationships can actually be used later.</p>
  
  <p>I have a little experience with relational databases but not much. I understand SQL queries and stuff like LEFT join, right join etc. And I've done some work in Access creating queries both with the GUI and by hand. But I've never created any relationships in the database itself. I tried this a minute ago in Access. After creating a relationship i tried adding my two test tables to a query, and the join was automatically created. </p>
  
  <p>However, when I actually looked at the actual SQL it did in fact include a JOIN command that was derived from the relationships. But that also means the query was not dependent at all on the relationship at all. How would a relationship be used in a database that doesn't have a drag and drop type query editor like Access?</p>
  
  <p>Is the only reason I would want to create a relationship in a database, or a DataRelation in a DataSet, is so that I can imply what relationships should exist but not necessarily force them?</p>