MERGE - WHEN MATCHED (for a table with 2 column that are the keys)

Question

Hi
I am using merge to insert/update a table whenever new records come in.
My question is if the table has 2 columns and both are a part of the primary key, do I need to have the merge statement "when matched" as well? Since both the columns are part of the key, when matched wont make sense here. I will only need when not matched, then insert.
Please correct if I am wrong.
Thx!

Answer 1

You need to be matchning/not matching on the whole primary key. Matched and not matched are required before 10G.
MERGE   INTO table1 loctab
       USING (SELECT colpk1,
                     colpk2,
                     col3,
                     col4
              FROM   table2) remtab
          ON (loctab.colpk1 = remtab.colpk1 AND loctab.colpk2 = remtab.colpk2)
WHEN MATCHED
THEN
  UPDATE SET loctab.col3 = remtab.col3,
                    loctab.col4 = remtab.col4
WHEN NOT MATCHED
THEN
  INSERT          (loctab.colpk1,
                       loctab.colpk2,
                       loctab.col3,
                       loctab.col4
  VALUES   (remtab.colpk1,
                remtab.colpk2,
                remtab.col3,
                remtab.col4
               );