My advice regarding the usability vs power issue is to have multiple stages. You'd have a DSL/query language that you parse, is secure, etc. And then you'd have a UI over the top of that which automatically creates the right queries.
The win here is that you then have an easy interface for 90% of users but the remainder with more bizarre or complex requirements can still get to where they want to go by either writing a query themselves in an "advanced" field of some sort, or you could even do it for them for $$$. Embedded JavaScript is an option here.
I would contrast this with something I would not advise, having a visual interface go straight to a database query behind the scenes.. because then you're basically limited to what you exposed in the UI.
The win here is that you then have an easy interface for 90% of users but the remainder with more bizarre or complex requirements can still get to where they want to go by either writing a query themselves in an "advanced" field of some sort, or you could even do it for them for $$$. Embedded JavaScript is an option here.
I would contrast this with something I would not advise, having a visual interface go straight to a database query behind the scenes.. because then you're basically limited to what you exposed in the UI.