title: How to check if a value from an array exists in an MySQL query
body: <p>I want to check if none of the days exist in <strong><code>custom_tag</code></strong> table of my database but the following code doesn't work. Can someone please tell me what I am doing wrong?</p>
  
  <pre><code>$tag_checker = $wpdb-&gt;get_results( "SELECT tag FROM custom_tag" );
  $days = array( 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday' );
  
  if( empty( array_intersect( $tag_checker, $days ) ) ) :
  // then do something
  endif;
  </code></pre>