preserving data after updates

[Scott Frankel <leknarf@xxxxxxxxxxx>]

Is there a canonical form that db schema designers use
to save changes to the data in their databases?

For example, given a table with rows of data, if I UPDATE
a field in a row, the previous value is lost.  If I wanted to
track the changes to my data over time, it occurs to me that
I could,

1) copy the whole row of data using the new value, thus
     leaving the old row intact in the db for fishing expeditions,
     posterity, &c.
     -- awfully wasteful, especially with binary data

2) enter a new row that contains only new data fields, requiring
     building a full set of data through heavy lifting and multiple 
queries
     through 'n' number of old rows
     -- overly complex query design probably leading to errors

3) create a new table that tracks changes
     -- the table is either wide enough to mirror all columns in
         the working table, or uses generic columns and API tricks to
         parse token pair strings, ...

4) other?

Thanks
Scott


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