title: Distinct values in an excel data source
body: <p>I have a source excel file where my "key" is held in column B. I want to add rows that contain different distinct key values to different tables in a database, using a list of datatables to allow for the number of distinct keys to be variable. </p>
  
  <p>Is it better practise to select the distinct records straight from the sheet itself, or to pull the entire sheet into a "master" datatable and query the datatable for my separate values? </p>