history rows management in database

Question

As in many databases, i am designing a database that should keep record of previous versions of the rows changed in each table.

The standard solution to this problem is

Answer 1

If I have 1 or 2 tables of history to keep I would do it exactly as Tuinstoel has suggested. But if you had dozens of tables to do this on I would move more toward a solution described by zendar. The reason is this.

How do you answer questions like,

• What changed since yesterday when everything was fine?

• Has user SMITHG made any changes?

Those questions require a one query per table, whether it's a separate _hist table or a partition inside the table. No matter, it's some huge list of queries. If you have a central table that looks like this, then it's a piece of pie.

table_name, Column_name, PK, Before_value, After_value, User, timestamp

Inserts have only after values,

Deletes have only before values,

Update have both but only for the columns which changed.

Some variations

You can include a column for I/U/D if you prefer You can exclude column values for Inserts and just record the PK and I since the correct values are still in the table.

Since this is Oracle you could partition on table_name, so in essence you actually do have one hist "table" per real table.

You can easily answer the above questions, which I believe are, quite simply, the most often asked questions. And it handles every question you can answer with partitions or _hist tables.