Question

On a old web app I had a table with the following structure:
tools(id, name, abbreviation, width, height, power, type)

The thing is that I need to add history support to the tools. The working scenario is that details of each tool can be modified, and I need to keep track of the changes. For example, if I need to see the details of a tool from a certain date from the past, how can I do that?

How the database have to looks?

Answer 1

I would keep the same table, but add a dateEffective field, and then create a new row every time a tool changes. Then when querying the table, you can get the version of a tool at a given date using:

SELECT * FROM tools WHERE id=@id AND dateEffective<@thisDate ORDER BY dateEffective DESC LIMIT (0,1)

EDIT You may wish to create another field called toolVersionId as a primary key.

EDIT 2 In response to your comment, how about:

SELECT *
FROM tools t1
WHERE toolVersionId IN (SELECT toolVersionId
                        FROM tools t2
                        WHERE t2.id = t1.id
                        ORDER BY t2.dateEffective DESC
                        LIMIT (0,1)
                       );