10 logical connections is a hard limit (see http://blogs.msdn.com/angelsb/archive/2005/01/13/352718.aspx and http://blogs.msdn.com/angelsb/archive/2004/09/07/226597.aspx for more details). If you go over this limit, it gets expensive from a performance standpoint. Also see ...

I guess that many people using UPDATE … FROM on a daily basis do so without being aware that they are violating all SQL standards.   All versions of the ANSI SQL standard that I checked agree that an UPDATE statement has three clauses – the UPDATE clause, naming the table to be updated; the SET clause, specifying the columns to change and ...

Relative comparison is a simple matter of human nature. From early childhood we compare and contrast what we see in the world around us, building a means by which to rate what we experience. And as it turns out, this desire to discover top and bottom, rightmost and leftmost, or best and worst happens to extend quite naturally into business ...

Prompted by a daily ''SQL Tip'' email a few days ago that recommended the correlated subquery to solve the cumulative total problem, this 5 minute screencast (5:02) demonstrates that the cursor solution indeed out-scales the set-based correlated subquery for this particular problem.

Within the SQL Server community, there is so much publicity on T-SQL set-oriented processing as good practice and the use of T-SQL cursors as bad practice that  T-SQL cursors are effectively being seen as a plague to be avoided when in fact it's not the use of T-SQ cursors, but their misuse, that should be avoided. To be fair, I must say that ...

Did you know that SQL Server allows stored procedures to have up to 2100 parameters? And more important: do you care? Well, some people do care, and Joe Celko seems to be one of them.   If you are a regular reader of SQL Server newsgroups, you probably know Joe Celko from his always unfriendly and often incorrect replies. Here is a typical ...

You have all seen websites where you can pick a bunch of categories by selection a bunch of check boxes. usually what you do is store those in a lookup table and then you create another table where you store all the categories for each customer. What if I tell you that you can store all that info in 1 row instead of 10 rows if a customer picked 10 ...

So I was doing some research on which is the best way to pass multiple-valued parameters into a stored procedure or user-defined function when I found some interesting results. I had always used a string-based user-defined function to parse a delimited list of values and I knew I could use XML to do the same thing, yet I had never compared the two ...

I was going to comment on Adam's post ''Medians, ROW_NUMBERs, and performance'' (which was a follow-up to Aaron's post ''Take the high road to middle ground'') and I realized that I needed to show some code and alas, comments are not so nice about formatting code, so I am posting a follow-up post... At the PASS Summit back in November, ...

A couple of days ago, Aaron Bertrand posted about a method for calculating medians in SQL Server 2005 using the ROW_NUMBER function in conjunction with the COUNT aggregate. This method (credited to Itzik Ben-Gan) is interesting, but I discovered an even better way to attack the problem in Joe Celko's Analytics and OLAP in SQL.Rather than using a ...