title: Update is updating more rows that it should
body: <p>I have a small table (145 rows) with a client ID column.  I am trying to use this table to determine what rows to update another table that has ~85000 rows.  I only want the matching 145 rows updated.</p>
  
  <p>When I do this query I see all the rows I expect to get updated (missing_names is the 145-row table):</p>
  
  <pre><code>SELECT *
  FROM MEMBER M
  JOIN missing_names MN
  ON MN.ID = M.ID
  WHERE MN.ID IS NOT NULL
  </code></pre>
  
  <p>I am trying to pull data from a different table and do the update like this:</p>
  
  <pre><code>UPDATE MEMBER
  SET LastName = R.Client_Last, 
  FirstName = R.Client_First, 
  Gender = 
  FROM Roster R
  JOIN missing_names MN
  ON MN.ID = R.Client_ID
  WHERE MN.ID IS NOT NULL
  </code></pre>
  
  <p>When I run this update statement I see the different IDs with the same first and last name.  The roster table has the correct names for a client ID.  I thought this type of update statement would only update a matching row in the member table from the matching row in the roster table?</p>