I will be the 1st to admit that I am no Itzik Ben-Gan when it comes to writing complex SQL statements and I wonder at times how people come up with some of the Selects that I see. Sometimes they are so complex or convoluted that I simply have a hard time figuring out the intent or the logic behind them. But as a performance consultant I pretty much find myself looking at these on a regular basis when they end up scanning very large tables or indexes. I find that many developers have a hard time splitting up the query into what I think are more manageable pieces, especially if there is a temp table involved. Lets face it temp tables are evil aren’t they :). Well that’s a whole another discussion which we won’t get into now but sometimes they can be be your friend. For instance today I took a rather unwieldy query that was being used in a stored procedure in which the optimizer simply couldn’t come up with an efficient query the way it was written. And one of the issues was that they needed a total count for paging purposes so they were running the same query twice, once for the count and once to get the TOP xx rows. In a nutshell I changed the query to use a UNION which allowed the optimizer to focus better on the SARG’s for each part of the query and placed the resultant rows into a temp table. This gave me the ability to get a count and retrieve the rows using TOP xx without running it twice. As you can see from the picture the costs were dramatic. The reads went from over 3 Million to just under 5 thousand and the duration went from over 23 seconds to 150 milliseconds. So bottom line is don’t be afraid to make the query more maintainable and break it up at times. You might be surprised what you can accomplish.