TIP: Row by Row operations without cursors
In general, cursors suck ass! Ok, that’s a bit extreme, but I have a long and ugly history with cursors. Let me diverge here and tell you a true story.
A while ago, a friend of mine recommended me to a company in serious need of senior developers for full-time or contract work. After talking to the dev manager over the phone, he felt my rate was too high, but wanted me to come in anyways. He set his top three developers in the room with me and left as they began to drill me with technical questions.
Now, I don’t mind being asked difficult technical questions in an interview. In fact, I think it’s a necessary part of an interview. But it was clear from the outset that these three hadn’t set their egos aside and they were quite antagonistic. One of them asked me the following question.
Suppose you have a table named
tblUser with column named FirstName.
On the whiteboard, construct a query that will select all the first
names into a single varchar with commas. I asked if I may assume that
the list of names will fit in a VARCHAR 8000, to which they replied yes.
So I promptly wrote the following on the board.
DECLARE @FirstNames VARCHAR(8000) SET @FirstNames = '' SELECT @FirstNames = FirstNames + ',' + @FirstNames FROM tblUser
With disdain on their faces, they shook their heads and said no. No! Well of course they did, they were looking for a cursor answer. They wanted to know if I could write a cursor. Needless to say, I didn’t get the job, but after the fact, I couldn’t help sending the manager an email informing him that not only was my answer correct, but it was 1000 times faster than the answer they wrote on the board. Yes, I’m still bitter. ;)
Which brings me back to the point of this post. If you can avoid a cursor solution, by all means do. The following article describes a technique for performing row by row operations without using a cursor. It makes several assumptions about your table, but for the most part, this is very useful.