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authorCarlo Zancanaro <carlo@clearboxsystems.com.au>2013-07-01 08:15:44 +1000
committerCarlo Zancanaro <carlo@clearboxsystems.com.au>2013-07-01 08:15:44 +1000
commitbe3302010635abd27adb64f58964baa7d205428e (patch)
treefda33646e70b4e52d1cc7868aac989e7a8ed8af2
parentcf3525b7e28fff70f9bf4a9151d1979226cd71f6 (diff)
Add union/intersection to the dsl
-rw-r--r--src/clojure_sql/compiler.clj38
-rw-r--r--src/clojure_sql/dsl.clj24
2 files changed, 43 insertions, 19 deletions
diff --git a/src/clojure_sql/compiler.clj b/src/clojure_sql/compiler.clj
index 6b3ec4a..d0b1206 100644
--- a/src/clojure_sql/compiler.clj
+++ b/src/clojure_sql/compiler.clj
@@ -223,24 +223,28 @@
(if drop
(str " OFFSET " drop)))))
+(def ^:private set-operations {:union "UNION", :intersect "INTERSECT"})
+
(defmulti compile-query (fn [db _] db) :default :postgres)
-(defmethod compile-query :postgres [db {:keys [tables fields joins where sort group having union take drop]}]
- (if union
- (->> union
- (map (partial compile-query db))
- (apply sequence)
- ((p-lift string/join " UNION ")))
- ($str (return "SELECT ")
- (compile-fields db fields)
- (if tables
- ($str (return " FROM ")
- (compile-tables db joins tables))
- ($str ""))
- (compile-where db where)
- (compile-group db group)
- (compile-having db having)
- (compile-sort db sort)
- (compile-limit db take drop))))
+(defmethod compile-query :postgres [db {:keys [tables fields joins where sort group having take drop set-operation queries]}]
+ (or (if set-operation
+ (let [op-str (str ") " (get set-operations set-operation) " (")]
+ (->> queries
+ (map (partial compile-query db))
+ (apply sequence)
+ ((p-lift string/join op-str))
+ $add-parentheses)))
+ ($str (return "SELECT ")
+ (compile-fields db fields)
+ (if tables
+ ($str (return " FROM ")
+ (compile-tables db joins tables))
+ ($str ""))
+ (compile-where db where)
+ (compile-group db group)
+ (compile-having db having)
+ (compile-sort db sort)
+ (compile-limit db take drop))))
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))