Anything that has to do with sorting your data.
I promise to get back to writing articles on a more regular basis soon, but in the meantime, here's a comment from Nathan A. on using DISTINCT and ORDER BY:
This is actually a problem I have been puzzling over for quite a while now. I actually need to do that sort. I wonder if I may have to create another column that has the list of ordering values in it in increasing order so for my example above assuming a letter table and a number table that contains the numbers for letters, the number table would not change but I...
Let's take a look at another one of those stupid, arbitrary SQL Server error messages that Bill Gates clearly only created because Micro$oft is evil and incompetent and they want to annoy us (and probably kill baby squirrels, too):
Msg 145, Level 15, State 1, Line 4
ORDER BY items must appear in the select list if SELECT DISTINCT is specified.
This message pops up when you ask for DISTINCT rows for one set of columns, but you'd like to have the results ordered by one or more columns not specified in your distinct set. For some reason, SQL Server will not allow...