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by z29LiTp5qUC30n
967 days ago
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sometimes called audit or journal tables. Every time something is updated or deleted, the entire previous record is inserted into its corresponding _A table with who did it and when (and optionally for what transaction number) so delete from foo results in an insert into foo_A before the delete occurs.
so update to bar results in an insert into bar_A before the update occurs
and rolling back a delete results in picking the old values out of the _A table
and rolling back an update results in picking the old values out of the _A table and inserting the current values into the _A table before the updating the main table. |
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