title: How to do Mysql Union with check if row exists?
body: <p>OK this is bit complicated because my tables are not referenced or combined or to be matched with each other so I cant use JOIN's. I am building a search form that would simply match search keyword in multiple tables. </p>
  
  <p>The issue I have is that I have to generate news item link depending from which table the result came but I cant find a hook. MySql union works perfect except that I cant check if data is from table a or table b. </p>
  
  <pre><code>here is short version 
  SELECT  i.title,i.category FROM table_a  WHERE REGEXP 'news'
  UNION 
  SELECT i.title,i.category FROM table_b WHERE REGEXP 'news'
  </code></pre>
  
  <p>now , my table A  has 36 rows  and table B  has 34  , one more difference is that table A  has row name extra_field  which I wanted to check and based on that switch my link. </p>
  
  <p>php switch after query could be something like </p>
  
  <pre><code>foreach($rows as $row) :
  if($row-&gt;extra_field):
  $link = 'index.php?".$row-&gt;category.$row-&gt;title".html'
  else:
  $link = 'index.php?".$row-&gt;title".html'
  endif;
  endforeach;
  </code></pre>
  
  <p>So is there a way to check in my UNION sql if that row exists? I know how to check if row exists but how to do that in UNION?</p>
  
  <p>Please help. Thank you!</p>