title: Adding conditions in MERGE statement in Oracle SQL for INSERT/UPDATE
body: <p>I have to insert/update some RECORDS in table target_table. These records are coming one source_table.</p>
  <p>I am using MERGE for update/insert the target_table.</p>
  <pre><code>MERGE
     INTO  target_table tgt
     USING source_table src
     ON  ( src.column1 = tgt.column1 and
           src.column2 = tgt.column2)
  WHEN MATCHED
  THEN
     UPDATE
     SET   tgt.column3= src.column3,
           tgt.column4 = src.coulmn4   
  WHEN NOT MATCHED
     THEN
  INSERT ( tgt.column1,
           tgt.column2,
           tgt.column3,
           tgt.column4 )
  VALUES ( src.coulmn1,
           src.coulmn2,
           src.coulmn3,
           src.coulmn4);
  </code></pre>
  <p>I want to add some specific condition on update.</p>
  <p><code>IF target_table.column3 in (val1','val2)</code></p>
  <p>then only there should be update, else no update or insert.</p>