I had a lot of trouble connecting to an MS SQL Server at work via Clojure. Java 6 comes with a JDBC-ODBC bridge which worked fine from a Clojure REPL at a command prompt, or from inferior-lisp in Emacs, but in SLIME it would hang every time I tried to connect and I'd have to kill Java. Couldn't for the life of me figure out why.

I got it to work eventually by using Microsoft's own JDBC driver, which you can download here.

Once you put the downloaded .jar file on your CLASSPATH (in my case, sqljdbc4.jar) you can connect like this:

user> (def db {:classname "com.microsoft.sqlserver.jdbc.SQLServerDriver"
               :subprotocol "sqlserver"
               :subname "//server_hostname;database=SomeDatabase;user=SomeUser;password=SomePassword"})
#'user/db
user> (use 'clojure.contrib.sql)
nil
user> (with-connection db 
        (with-query-results rs ["SELECT * FROM whatever"] (prn rs)))
... results ...

Posted for the sake of Googlebot and for my own future sanity.