T-SQL Tuesday #1: Date/Time Tricks

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I’m going to try out Adam Machanic’s idea for a blog party. The topic this month are Date/Time tricks.

Instead of supplying a trick for Date/Time, I’m going to caution you about the tricks that you use. Let’s take a simple issue. You want to pull back data from a table, let’s use the Production.TransactionHistoryArchive in AdventureWorks2008, for a given month of data. Before we run the query, let’s create an index on the table:

The query itself is pretty simple. This is one mechanism that will retrieve the data for the month of July in 2003:

In theory you should be able to use the index that was created earlier, but instead, you’ll see this execution plan:

The problem is occuring because there is a function running against the columns. This is going to force a scan, even though you have a good index. Rewriting the query so that it looks like this:

Eliminates the function on the column so that the execution plan is now a nice clean index seek:

Whatever tricks you begin to apply to date/time, be careful of how you apply them. And, if you try a fix like I supplied above, be sure it returns the data you think it returns, testing is the key to applying anything you read on the internet.


OK, fine, but what do you think?