title: mysql, select two tables, then merge results
body: <p>I have two tables.</p>
  
  <pre><code>table_A
    A    
    ---- 
    a    
    b    
    c    
    d    
  
  
  table_B
    B    
    ---- 
    1    
    2    
  </code></pre>
  
  <p>and want to select it like below</p>
  
  <pre><code>  A      B   
    ----  ---- 
    a      1
    b      2
    c     null
    d     null
  </code></pre>
  
  <p>How can I make such a select.
  Do I need procedure? or just need 'join syntax'?
  Please help me.</p>