Thursday, December 14, 2017

TSQL Tuesdays # 45

It is time for another TSQL Tuesday - Mickey Stuewe (blog | twitter) is hosting this month and the topic is "Invitation–Follow the Yellow Brick Road". Well, here it goes..

I worked for a medical device company that needed to audit quite a bit of data. I was lucky enough to work with some wonderful and talented people. One of those persons was the DBA. I took what he did and said as database gospel. He was the type of person who would help you understand things if you asked - and if he didn't know he would tell you, but get back to you later with an answer. He probably got sick of seeing me as often as he did. :) When I started at that company, I knew that I had enough understanding to be dangerous, but I also knew full well and good that I had a LOT to learn. I took the opportunity to learn from him.

He set up a system of auditing using triggers on MANY tables in the transactional database. I started learning everything I could about using the different types of triggers (insert, update, delete) and the way to use the system tables to put the data here and there, and to record what happened and by whom. I ended up learning a lot of "magic behind the curtain" about SQL and triggers along the way.  When I was hired, the database used was SQL 2000 (we later went through a couple of upgrades - the validation was a lot of work). I never even thought about other options for auditing - this solution worked well, why wouldn't everyone use it. :)

When I started at my current job, I realized my passion for SQL. I knew I liked it before, but this job has really given me an opportunity to get my hands dirty much more. That is when I was introduced to the ETL and the data warehouse. I had been introduced to the concept of a warehouse before, so that wasn't new, but I hadn't been involved in the manipulations and loading of data.

In doing research about ETL in general, I learned about Change Data Capture (CDC) and Change Tracking. I have to admit, I was initially a little bummed. I had learned something that was working very well, but here was this new functionality that had the same end result, just worked differently. I eventually learned quite a bit more about it and was thrilled with the possibilities. I wanted to start using CDC with the ETL to help with incremental loading. I haven't gotten my chance and might not be able to since we are phasing out the only data source that we house internally - all other data comes from outside vendors by either files or database backups. Therefore, I put the thought of auditing on the back burner.

Recently, however, we had a need on the application development side, to audit who made certain changes. BINGO - perfect timing - I had already done the research previously, so I knew how to implement things to get what we needed up and running pretty quickly. Of course, as everything else, other priorities have slipped in, but I am almost done with the implementation. Setting up the CDC portion was a snap, getting the data where I want it so I can use it is what is taking more time. I am taking the audited records and putting the changes into an XML string then saving that in a central repository for audit logging and reporting (but yet keeping it dynamic so I can have 1 script no matter what the data structure of the audited table looks like).

In summary, I learned a lot from looking into what made the first auditing process I was exposed to "tick". Then, I learned more about changes in functionality between SQL 2000 and SQL 2008 R2.

I didn't know about the SQL community until a year ago (Thank you - SQL Saturday in Baton Rouge 2012). I have met some wonderful people so far and look forward to meeting even more! All in all, it is really awesome to say that while I don't have the "admin" type of historical knowledge a lot of people do, the auditing topic is something where I can say I understand the before and after.

Thank you Mickey for such a great topic - and talk to you soon!

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