## 數據庫 Clojure Contrib里面的jdbc庫簡化了clojure對于關系型數據庫的訪問. 它通過commit和rollback來支持事務, 支持prepared statements, 支持創建/刪除表, 插入/更新/刪除行, 以及查詢。下面的例子鏈接到一個Postgres 數據庫并且執行了一個查詢。代碼的注釋里面還提到了怎么使用jdbc來連接mysql。 ``` (use 'clojure.java.jdbc) (let [db-host "localhost" db-port 5432 ; 3306 db-name "HR"] ; The classname below must be in the classpath. (def db {:classname "org.postgresql.Driver" ; com.mysql.jdbc.Driver :subprotocol "postgresql" ; "mysql" :subname (str "//" db-host ":" db-port "/" db-name) ; Any additional map entries are passed to the driver ; as driver-specific properties. :user "mvolkmann" :password "cljfan"}) (with-connection db ; closes connection when finished (with-query-results rs ["select * from Employee"] ; closes result set when finished ; rs will be a non-lazy sequence of maps, ; one for each record in the result set. ; The keys in each map are the column names retrieved and ; their values are the column values for that result set row. (doseq [row rs] (println (row :lastname)))))) ``` `clj-record` 提供了一個類似 Ruby on Rails的ActiveRecord的數據庫訪問包. 更多關于它的信息看這里： [http://github.com/duelinmarkers/clj-record/tree/master](http://github.com/duelinmarkers/clj-record/tree/master) .