title: Cannot establish one-to-many relationship in Power BI
body: <p>I have currently two tables in my Power BI model:</p>
  
  <p>Clients and Client Visits</p>
  
  <p>Both are imports from an SQL server.</p>
  
  <p>I unduplicated the "Clients Table" to eliminate erroneous double entries.</p>
  
  <p>When I try to establish a one-to-many relation based on social security numbers I get the following message:</p>
  
  <p>"The cardinality you selected isn't valid for this relationship".</p>
  
  <p>BTW, I set the "Cross filter direction" as: "Single (Clients Table filters Client Visits)".</p>
  
  <p>Any advice as to how to solve this problem is appreciated.</p>