Fumiko Hanreich’s talk at Clojure/West is about HoneySQL, a Clojure DSL for representing SQL queries.
People in the Clojure community talk a lot about representing things as data. This is an approach inherited from its Lisp forebears. HoneySQL is a data-oriented DSL that represents SQL queries. You build up SQL statements in a structured form, not string concatenation.
HoneySQL is a good example of a case where the Clojure philosophy allows for a solution to an existing problem. The problem is that SQL is designed as a human-facing language. That’s fine by itself, but it is not a good language for composing pieces of a query into a larger query–the kind of things a program would do. HoneySQL provides an intermediate representation that is way more amenable to manipulation. In a way, it does the same thing for SQL as Lisp s-expressions did for code.