add `ResultSet#exec` to ensure the query is performed. By default generates a `move_next`.

spec/std/db/db_spec.cr

@@ -50,4 +50,12 @@ describe DB do
       db.connection.last_statement.closed?.should be_true
     end
   end
+
+  it "exec should perform statement" do
+    with_dummy do |db|
+      db.exec ""
+      DummyDriver::DummyResultSet.last_result_set.executed?.should be_true
+      db.connection.last_statement.closed?.should be_true
+    end
+  end
 end

spec/std/db/dummy_driver.cr

@@ -43,9 +43,20 @@ class DummyDriver < DB::Driver
   class DummyResultSet < DB::ResultSet
     def initialize(statement, @iterator)
       super(statement)
+      @executed = false
+      @@last_result_set = self
+    end
+
+    def self.last_result_set
+      @@last_result_set.not_nil!
+    end
+
+    def executed?
+      @executed
     end
 
     def move_next
+      @executed = true
       @iterator.next.tap do |n|
         return false if n.is_a?(Iterator::Stop)
         @values = n.each

src/db/result_set.cr

@@ -15,6 +15,12 @@ module DB
       @statement.close
     end
 
+    # :nodoc:
+    # Ensures it executes the query
+    def exec
+      move_next
+    end
+
     abstract def move_next : Bool
 
     # TODO def empty? : Bool, handle internally with move_next (?)

src/db/statement.cr

@@ -7,7 +7,9 @@ module DB
     end
 
     def exec(*args)
-      execute(*args).close
+      query(*args) do |rs|
+        rs.exec
+      end
     end
 
     def scalar(*args)