title: SQL - Check if all the columns in one table also exist in another
body: <p>I have 2 tables (say A and B) in a MS SQL DB representing customer transactions. Both share a column (say Column X).</p>
  
  <p>Ideally information in table B is a subset of information in table A.</p>
  
  <p>Can I run a SQL query to check based on Column X if all the values in Table B are present in Table A?</p>
  
  <p>Thanks</p>