I've been using a "common" style for my reports for quite a while. I include a report title, then below that I usually have one or more lines which show which filter and sorting criteria were used to generate the report. I include a page X/Y line, usually in the bottom right hand side of the report. At some point I started adding the print date/time, who it was printed by, and the name of the file of the report. All of these fields together have been valuable when making changes and in determining why something isn't working.

The other day I had someone bring a report that was generated last year for the first 6 months of 2007 by an employee who is no longer with the company. They were attempting to tie the summarized numbers back to the detail which generated them and weren't sure how to find the detail. We had recently changed a fundamental aspect of how this particular report and supporting (detail) reports generated some of their numbers so I decided to just run a query against the database to get the information they were looking for. I looked at the timeframe the report was run for and wrote the query - there were no filters so it was really straightforward, or so I thought. When I totaled up the numbers they didn't match the report. Uh oh. I started worrying about what kinds of bad things might have happened that would have changed our historical tables.

Ugh...Then I noticed that the report was printed on the ending date of the report (in this case, it was run for 1/1/2007 - 6/28/2007) and it was printed on 6/28/2007. The light bulb went on. This particular report showed numbers that weren't available until a few months after the month they were applicable to. Essentially, we don't get numbers for January until March (even though they are posted back into January). So when this report was run, the numbers for April forward weren't available yet and weren't included in the report (even though the report range said it was through 6/28/2007). In the meantime those numbers had been posted and since I was pulling these numbers a year later they appeared in my version. I adjusted my query to exclude numbers posted after the report run date/time and suddenly everything balanced. Without knowing when the report was run it would have taken a LOT of work to resolve this (I'm not even sure I would have been able to).

Are there any types of things you're including on reports which have saved you?

In addition to the fields mentioned above, I've recently started including a "key" at the bottom of a number of reports which explain how numbers are generated and a more detailed explanation of their meaning. As questions come up about them I adjust my descriptions so they answer the questions asked. I'm using a really tiny font to keep the amount of space lost to them to a minimum but I'm finding they have also been really valuable since I'm not having to refer to the code as much to explain how some numbers were derived. It also addresses the issue where you use common names for column headers on various reports but the underlying numbers in those columns are actually inclusive or exclude different things.