Problem

A bulk update runs successfully but updates every matching row, even when the value has not changed. This increases locking, transaction log usage, and can trigger unnecessary downstream processes.

Solution

Add a comparison condition so only genuinely changed rows are updated.

UPDATE t
SET t.some_column = tu.new_some_column
FROM target_table t
JOIN #temp_updates tu ON tu.id = t.id
WHERE
    t.some_column <> tu.new_some_column
    OR t.some_column IS NULL;

Notes

• Reduces transaction log growth during large updates.
• Minimises locking and index churn.
• Particularly useful when updates trigger audit logs or change tracking.
• Always preview with a SELECT first:

SELECT *
FROM target_table t
JOIN #temp_updates tu ON tu.id = t.id
WHERE
    t.some_column <> tu.new_some_column
    OR t.some_column IS NULL;