Merge pull request #217 from jkk/MichaelBlume-delete

Add multi-table DELETE that takes a FROM clause

README.md

@@ -204,6 +204,22 @@ Deletes look as you would expect:
 => ["DELETE FROM films WHERE kind <> ?" "musical"]
 ```
 
+If your database supports it, you can also delete from multiple tables:
+
+```clojure
+(-> (delete [:films :directors])
+    (from :films)
+    (join :directors [:= :films.director_id :directors.id])
+    (where [:<> :kind "musical"])
+    sql/format)
+=> [#sql/regularize
+    "DELETE films, directors
+     FROM films
+     INNER JOIN directors ON films.director_id = directors.id
+     WHERE kind <> ?"
+    "musical"]
+```
+
 Queries can be nested:
 
 ```clojure

src/honeysql/format.cljc

@@ -205,6 +205,7 @@
    :select 50
    :insert-into 60
    :update 70
+   :delete 75
    :delete-from 80
    :columns 90
    :from 110
@@ -588,6 +589,9 @@
 (defmethod format-clause :delete-from [[_ table] _]
   (str "DELETE FROM " (to-sql table)))
 
+(defmethod format-clause :delete [[_ tables] _]
+  (str "DELETE " (comma-join (map to-sql tables))))
+
 (defn cte->sql
   [[cte-name query]]
   (str (binding [*subquery?* false]

src/honeysql/helpers.cljc

@@ -271,6 +271,13 @@
   ([table] (delete-from nil table))
   ([m table] (build-clause :delete-from m table)))
 
+(defmethod build-clause :delete [_ m tables]
+  (assoc m :delete tables))
+
+(defn delete
+  ([tables] (delete nil tables))
+  ([m tables] (build-clause :delete m tables)))
+
 (macros/usetime
  (defhelper with [m ctes]
    (assoc m :with ctes)))

test/honeysql/format_test.cljc

@@ -200,3 +200,17 @@
           :set  {:a 1}
           :where  [:= :bar.b 42]}
          (format :quoting :mysql)))))
+
+(deftest delete-from-test
+  (is (= ["DELETE FROM `foo` WHERE `foo`.`id` = ?" 42]
+         (-> {:delete-from :foo
+              :where [:= :foo.id 42]}
+             (format :quoting :mysql)))))
+
+(deftest delete-test
+  (is (= ["DELETE `t1`, `t2` FROM `table1` `t1` INNER JOIN `table2` `t2` ON `t1`.`fk` = `t2`.`id` WHERE `t1`.`bar` = ?" 42]
+         (-> {:delete [:t1 :t2]
+              :from [[:table1 :t1]]
+              :join [[:table2 :t2] [:= :t1.fk :t2.id]]
+              :where [:= :t1.bar 42]}
+             (format :quoting :mysql)))))