Merge pull request #76 from cddr/add-support-for-exists-clause

[#75] Add support for exists

.gitignore

@@ -11,4 +11,5 @@ pom.xml*
 .nrepl-port
 .classpath
 .project
+.nrepl-port
 bin

CHANGES.md

@@ -1,5 +1,6 @@
 ## 0.5.3 In development
 
+* Support exists syntax (@cddr)
 * Support locking selects (@dball)
 * Add sql array type and reader literal (@loganmhb)
 * Allow user to specify where in sort order NULLs fall (@mishok13)

src/honeysql/format.clj

@@ -350,13 +350,18 @@
     (to-sql pred)
     (let [[op & args] pred
           op-name (name op)]
-      (if (= "not" op-name)
-        (str "NOT " (format-predicate* (first args)))
-        (if (#{"and" "or" "xor"} op-name)
-          (paren-wrap
-           (string/join (str " " (string/upper-case op-name) " ")
-                        (map format-predicate* args)))
-          (to-sql (apply call pred)))))))
+      (case op-name
+        "not" (str "NOT " (format-predicate* (first args)))
+
+        ("and" "or" "xor")
+        (paren-wrap
+         (string/join (str " " (string/upper-case op-name) " ")
+                      (map format-predicate* args)))
+
+        "exists"
+        (str "EXISTS " (to-sql (first args)))
+
+        (to-sql (apply call pred))))))
 
 (defmulti format-clause
   "Takes a map entry representing a clause and returns an SQL string"
@@ -370,6 +375,9 @@
 (defmethod format-clause :default [& _]
   "")
 
+(defmethod format-clause :exists [[_ table-expr] _]
+  (str "EXISTS " (to-sql table-expr)))
+
 (defmethod format-clause :select [[_ fields] sql-map]
   (str "SELECT "
        (when (:modifiers sql-map)

test/honeysql/format_test.clj

@@ -34,6 +34,16 @@
   (is (= (format-clause (first {:insert-into [[:foo [:a :b :c]] {:select [:d :e :f] :from [:baz]}]}) nil)
          "INSERT INTO foo (a, b, c) SELECT d, e, f FROM baz")))
 
+(deftest exists-test
+  (is (= (format {:exists {:select [:a] :from [:foo]}})
+         ["EXISTS (SELECT a FROM foo)"]))
+  (is (= (format {:select [:id]
+                  :from [:foo]
+                  :where [:exists {:select [1]
+                                   :from [:bar]
+                                   :where :deleted}]})
+         ["SELECT id FROM foo WHERE EXISTS (SELECT 1 FROM bar WHERE deleted)"])))
+
 (deftest array-test
   (is (= (format {:insert-into :foo
                   :columns [:baz]