Database design for audit logging [closed]

One method that is used by a few wiki platforms is to separate the identifying data and the content you’re auditing. It adds complexity, but you end up with an audit trail of complete records, not just listings of fields that were edited that you then have to mash up to give the user an idea of what the old record looked like.

So for example, if you had a table called Opportunities to track sales deals, you would actually create two separate tables:

Opportunities_Content (or something like that)

The Opportunities table would have information you’d use to uniquely identify the record and would house the primary key you’d reference for your foreign key relationships. The Opportunities_Content table would hold all the fields your users can change and for which you’d like to keep an audit trail. Each record in the Content table would include its own PK and the modified-by and modified-date data. The Opportunities table would include a reference to the current version as well as information on when the main record was originally created and by whom.

Here’s a simple example:

CREATE TABLE dbo.Page(  
    ID int PRIMARY KEY,  
    Name nvarchar(200) NOT NULL,  
    CreatedByName nvarchar(100) NOT NULL, 
    CurrentRevision int NOT NULL, 
    CreatedDateTime datetime NOT NULL

And the contents:

CREATE TABLE dbo.PageContent(
    PageID int NOT NULL,
    Revision int NOT NULL,
    Title nvarchar(200) NOT NULL,
    User nvarchar(100) NOT NULL,
    LastModified datetime NOT NULL,
    Comment nvarchar(300) NULL,
    Content nvarchar(max) NOT NULL,
    Description nvarchar(200) NULL

I would probably make the PK of the contents table a multi-column key from PageID and Revision provided Revision was an identity type. You would use the Revision column as the FK. You then pull the consolidated record by JOINing like this:

JOIN PageContent ON CurrentRevision = Revision AND ID = PageID

There might be some errors up there…this is off the top of my head. It should give you an idea of an alternative pattern, though.

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