title: skip/ignore/don't insert duplicate rows
body: <p>Here's what I want:
  Copy rows from tableA to tableB, but not any rows that are already in tableB. there is no PK or identiy, i simply want to check on each field, and don't insert if there's a matching row with all the same fields.  I've tried with both INSERT and MERGE:</p>
  
  <pre><code> --try with INSERT
   INSERT TableB(col1,col2,col3,col4,col5,col6, etc.)
   SELECT (col1,col2,col3,col4,col5,col6, etc.)  
   FROM tableA as src
   WHERE NOT EXISTS (SELECT 1 FROM TableB as T
              WHERE               
              T.col1 = src.col1 AND
              T.col2 = src.col2 AND
              T.col3 = src.col3 AND
              T.col4 = src.col4 AND
              T.col5 = src.col5 AND
              T.col6 = src.col6, etc.)
  </code></pre>
  
  <p>I've also tried with MERGE:</p>
  
  <pre><code>  MERGE INTO tableA src
    USING tableB T
    ON (
              T.col1 = src.col1 AND
              T.col2 = src.col2 AND
              T.col3 = src.col3 AND
              T.col4 = src.col4 AND
              T.col5 = src.col5 AND
              T.col6 = src.col6, etc.)
    WHEN NOT MATCHED THEN
    INSERT (col1,col2,col3,col4,col5,col6, etc.)
    VALUES (col1,col2,col3,col4,col5,col6, etc.);
  </code></pre>
  
  <p>Both do exactly the same thing: I'll do the insert (or merge), and initially all rows get imported, which is good, but then on second attempt (which should insert/merge 0 rows) it will insert/merge 60% of the rows.</p>
  
  <p>I believe the issue is because I don't have a PK which is what i've seen on other posts here.  I just want to match on all fields though, is that possible?  Am i missing something?</p>
  
  <p>Thanks for any advise/direction!</p>