title: Trying to convert UPDATE into MERGE
body: <p>My question is simple. I am trying to convert an UPDATE statement into MERGE statement for better performance, as the update count maybe between 10K - 1M. Here is my UPDATE code:</p>
  
  <pre><code>UPDATE table_1 t1
     SET t1.col_1 =
            (SELECT t2.name
               FROM table_2 t2
              WHERE t2.fn = t1.col_1),
         t1.Col_3 =
            (SELECT t2.name
               FROM table_2 t2
              WHERE t2.fn = t1.Col_3),
         t1.Col_5 =
            (SELECT t2.name
               FROM table_2 t2
              WHERE t2.fn = t1.Col_5);
  </code></pre>
  
  <p>I tried changing into MERGE:</p>
  
  <pre><code>MERGE INTO Table_1
       USING (SELECT NAME FROM table_2) A
          ON (1 = 1)
  WHEN MATCHED
  THEN
     UPDATE SET Table_1.col_1 = A.NAME,
                Table_1.col_3 = A.NAME,
                Table_1.col_5 = A.NAME;
  </code></pre>
  
  <p>The above code throws error, please help me sort the problem out. Thanks in advance.</p>