Add union/intersection to the dsl

1 files changed, 22 insertions, 2 deletions

diff --git a/src/clojure_sql/dsl.clj b/src/clojure_sql/dsl.clj
index 6ba81bc..0a05763 100644
--- a/src/clojure_sql/dsl.clj
+++ b/src/clojure_sql/dsl.clj
@@ -177,7 +177,8 @@
   (and (nil? (:group query))
        (nil? (:having query))
        (nil? (:take query))
-       (nil? (:drop query))))
+       (nil? (:drop query))
+       (nil? (:set-operation query))))
 
 (defn ^:private convert-to-subquery [query]
   (-> (table query)
@@ -195,7 +196,7 @@
 
 (def ^:private valid-join-type? (comp boolean #{:cross :inner :outer :full-outer}))
 (defn join
-  "Join two queries into one query The fields of the resultant query
+  "Join two queries into one query. The fields of the resultant query
   will be the union of the argument queries.
 
   If `type` is not provided then the join type will be automatically
@@ -376,3 +377,22 @@
     (if-let [old-drop (:drop query)]
       (assoc query :drop (+ old-drop n))
       (assoc query :drop n))))
+
+(defn ^:private union-compatible? [& queries]
+  (apply = (map (comp set keys :fields) queries)))
+
+(defn union
+  "Combine the results of two queries"
+  [& queries]
+  (assert (apply union-compatible? queries) "Unioned queries must expose the same fields.")
+  (assoc (q/->Query)
+    :set-operation :union
+    :queries queries))
+
+(defn intersection
+  "Take the common rows in two queries"
+  [& queries]
+  (assert (apply union-compatible? queries) "Unioned queries must expose the same fields.")
+  (assoc (q/->Query)
+    :set-operation :intersect
+    :queries queries))