title: pl sql. 0 rows merged
body: <p>I am new to <code>merge</code> so this question may appear too dumb.</p>
  
  <p>I'm running </p>
  
  <pre><code>MERGE INTO regions r
     USING regions_temp t
     ON (r.id_region = t.id_region)
      WHEN NOT MATCHED THEN INSERT (r.id_region, r.region_name)
       VALUES (t.id_region, t.region_name);
  </code></pre>
  
  <p>Before I run the command the tables have following records (id_region, region_name):</p>
  
  <p>Regions: </p>
  
  <pre><code>1   1   Kiev
  2   2   Asia
  3   3   Australia
  4   4   South America
  5   5   Africa
  </code></pre>
  
  <p>Regions_temp:</p>
  
  <pre><code>1   1   
  2   2   Asia
  3   3   Australia
  4   4   South America
  </code></pre>
  
  <p>The command runs successfully but on the bottom of the window it says <strong>0 rows merged</strong> and no records are merged. </p>
  
  <p>Little help?</p>