I assumed that updates would not fail. If updates can fail, too, then you're pretty much stuck going through row-by-row. You could at least determine which rows should be inserts and which should be updates, in advance, by checking whether a corresponding row exists in the real table: 
$to_insert_stmt = q{
SELECT * FROM scratch S
WHERE session_id = ? AND NOT EXISTS (
  SELECT 1 FROM real_data
  WHERE key_val1 = S.key_val1 AND ...
)
};
$to_update_stmt = q{
SELECT * FROM scratch S
WHERE session_id = ? AND EXISTS (
  SELECT 1 FROM real_data
  WHERE key_val1 = S.key_val1 AND ...
)
};

[download]
Then any rows that fail insert are skips, and any rows that fail update are skips, and you don't waste time trying to insert rows that should be updates.
Caution: Contents may have been coded under pressure.

In reply to Re^3: Superior way to update SQL tables by Roy Johnson
in thread Superior way to update SQL tables by radiantmatrix

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