adamg 27214 (9/10/2012)
Using a function on a column in a where clause will not allow your query to use an index. That is why instead of isnull you want to use "Where col1 = 'a' OR Col1 IS NULL..."
Roger that. Most of the querying I do is ad-hoc on small datasets and the isnull function is a personal "at-a-glance" way for me to see that I'm including the null results on the RIGHT table (Bad habit? Yes. In production? No). For me it's easier when I'm troubleshooting because the less "OR" and "AND" structures I have to logic my way through during a troubleshooting session the better off I am. Thanks for pointing that out though. I constantly feel like I learn something on this site. I'm still amazed that I never realized two result sets are produced by just moving something from the WHERE clause up to the ON clause. I felt a "click" in my brain today and at 40 years of age I thought I was getting past most of those. It's good to know I can still learn. 😛