I am the author of SQL Fiddle, an online environment for testing and sharing database problems. The target audience for my site is for pretty technically-sophisticated users (database programmers, basically). One of the features I've implemented recently has been the source of some confusion, however, and I'm not sure how to make the whole concept more clear.
Please see this StackOverflow answer for a perfect example of this particular problem:
As I mention there, the problem is that there are two competing functions at play when you execute queries in my left-side panel. One function is the breakup of the individual statements executed, so that I can fetch and display the results from each statement in the below section. The other function is that sometimes, I need to run statements together as a "batch", so things like variables (as in the above example) get executed together.
The current solution to accomodate both functions is to change your "Query Terminator". This is a special character (or character combination) that is used to define the end of a query batch. I allow users to indicate which query terminator they would like to use by selecting it from a dropdown button (see the [ ; ] button on the site). This works, but few people seem to understand how to use this button to change the behavior of their query execution.
I built this button the way I did because I didn't have a ton of screen space to work with and this is a not-often needed function. However, I clearly need to do more make it obvious about how to use this. My very smart users are getting baffled by the error messages or strange behaviors that this function was intended to resolve.
Some things I've thought of:
I could show the actual query statements being executed for each result set; this would make it clear what exactly was being used to produce each one, and would lead the users to recognize the problem as one of query termination.
I could write up a FAQ/Help section that covers this function (and others), however I don't really have anything like this currently and I'd prefer to find a mechanism that was intuitive enough so that reading the help manual wouldn't be necessary.
I could use a bootstrap tooltip that came up when hovering over the button that attempts to explain this briefly.