Mickey's T-SQL Ponderings

Rick Krueger (b|t) is hosting this month’s T-SQL Tuesday blog party. The party was started by Adam Machanic (b|t) in December of 2009.  The topic this month is a fun one. He has asked us to write about a Rube Goldberg type of solution (aka a hack job) we created at some point in our careers.

Like many of you I worked at a Start-up back in 2000, but I wasn’t a database developer back then. Back then I was a web developer who specialized in the business layer which I wrote in VB and later VB.net. Back then I never thought about consulting with the DBA to see if my idea was good idea from a database point of view. I can tell you that I shudder at the mere thought of the “brilliant” solution I came up with back then…It was actually a great idea…until you put in a database and queried it.

The Plan

The company I worked for was building a shopping cart from the ground up. We needed a way to keep track of the state of each item in an Order and display that information at the Order level. My idea was to keep track of each Order Item state with an alphanumeric letter and we would string them all together into one field at the Order level so that we could query for Orders with Items at a particular state. (This is where we all shudder.)

When I thought of the idea, I thought there would only be a couple of letters. R for return, O for ordered, C for Canceled, etc. As we started going through all the permutations we found a ton of exceptions. I think by the time I handed the responsibilities over for this one field, we had almost 10 different designations.

The Flaw

Since (back then) I could read execution plans as well as I could read Japanese (which means not at all), I had no idea the impact of my design. I didn’t know that indexes on that field would become pretty much useless since a Like operator would have to be used to find a particular part of  the concatenated field.

A better approach for this same solution would be to leave the designations at the item level and for reporting concatenate the values at the Order level.

Second Verse, Same as the First

Since I never learned at the first company that my idea was flawed from a database perspective, I pitched the same plan at the next company…where we implemented it…again. I have learned my lesson since then and advocate to all .net developers that working with the DBA or DBD from the beginning can help achieve a better application.

Thanks for all the fish

Thanks go out to Rick Krueger for hosting this month’s T-SQL Tuesday blog party. Please visit his website at http://www.dataogre.com.