How can I implement user-friendly boolean logic in a web form GUI?

Question

Currently I have a web application where a user can use dropdown lists to generate SQL SELECT statements like so:

Column Select Dropdown | Operator Dropdown (= != >

Answer 1

Another option is something like SQL Server Management Studio query builder interface - several rows and columns, where rows represents ANDs, and columns ORs (or vice versa, I don't remember).

You can do real-time update of resulting query to help users (just like SQL Server updates the resulting SQL).