title: postgresql join query
body: <p>I have two tables T1 and T2</p>
  
  <pre><code>T1
  -id
  -columnA
  -columnB
  -columnC
  
  T2
  -id
  -columnX
  -columnY
  -columnZ
  </code></pre>
  
  <p>I have a query like </p>
  
  <pre><code>Select t1.* t2.columnZ 
  from T1 t1 
    left join on T2 t2 on t1.id = t2.id 
  where t2.columnZ = 'test'
  </code></pre>
  
  <p>I want result like if "where t2.columnZ = 'test'" does not return any row then it should return value of columnZ as null value</p>