diff --git a/spec/statement_spec.cr b/spec/statement_spec.cr
index a080b35..f70937e 100644
--- a/spec/statement_spec.cr
+++ b/spec/statement_spec.cr
@@ -51,6 +51,25 @@ describe DB::Statement do
     end
   end
 
+  it "allows no arguments" do
+    with_dummy_connection do |cnn|
+      stmt = cnn.prepared("the query").as(DummyDriver::DummyStatement)
+      stmt.query
+      stmt.params.should be_empty
+    end
+  end
+
+  it "concatenate arguments" do
+    with_dummy_connection do |cnn|
+      stmt = cnn.prepared("the query").as(DummyDriver::DummyStatement)
+      stmt.query 1, 2, args: ["a", [1, nil]]
+      stmt.params[0].should eq(1)
+      stmt.params[1].should eq(2)
+      stmt.params[2].should eq("a")
+      stmt.params[3].should eq([1, nil])
+    end
+  end
+
   it "should initialize positional params in query with array" do
     with_dummy_connection do |cnn|
       stmt = cnn.prepared("the query").as(DummyDriver::DummyStatement)
@@ -89,6 +108,25 @@ describe DB::Statement do
     end
   end
 
+  it "allows no arguments" do
+    with_dummy_connection do |cnn|
+      stmt = cnn.prepared("the query").as(DummyDriver::DummyStatement)
+      stmt.exec
+      stmt.params.should be_empty
+    end
+  end
+
+  it "concatenate arguments" do
+    with_dummy_connection do |cnn|
+      stmt = cnn.prepared("the query").as(DummyDriver::DummyStatement)
+      stmt.exec 1, 2, args: ["a", [1, nil]]
+      stmt.params[0].should eq(1)
+      stmt.params[1].should eq(2)
+      stmt.params[2].should eq("a")
+      stmt.params[3].should eq([1, nil])
+    end
+  end
+
   it "should initialize positional params in scalar" do
     with_dummy_connection do |cnn|
       stmt = cnn.prepared("the query").as(DummyDriver::DummyStatement)
diff --git a/src/db.cr b/src/db.cr
index 915e7b8..bbe0e3d 100644
--- a/src/db.cr
+++ b/src/db.cr
@@ -181,6 +181,7 @@ end
 
 require "./db/pool"
 require "./db/string_key_cache"
+require "./db/enumerable_concat"
 require "./db/query_methods"
 require "./db/session_methods"
 require "./db/disposable"
diff --git a/src/db/enumerable_concat.cr b/src/db/enumerable_concat.cr
new file mode 100644
index 0000000..3f70b0d
--- /dev/null
+++ b/src/db/enumerable_concat.cr
@@ -0,0 +1,38 @@
+module DB
+  # :nodoc:
+  struct EnumerableConcat(S, T, U)
+    include Enumerable(S)
+
+    def initialize(@e1 : T, @e2 : U)
+    end
+
+    def each
+      if e1 = @e1
+        @e1.each do |e|
+          yield e
+        end
+      end
+      if e2 = @e2
+        e2.each do |e|
+          yield e
+        end
+      end
+    end
+
+    # returns given `e1 : T` an `Enumerable(T')` and `e2 : U` an `Enumerable(U') | Nil`
+    # it retuns and `Enumerable(T' | U')` that enumerates the elements of `e1`
+    # and, later, the elements of `e2`.
+    def self.build(e1 : T, e2 : U)
+      return e1 if e2.nil? || e2.empty?
+      return e2 if e1.nil? || e1.empty?
+      EnumerableConcat(Union(typeof(sample(e1)), typeof(sample(e2))), T, U).new(e1, e2)
+    end
+
+    private def self.sample(c : Enumerable?)
+      c.not_nil!.each do |e|
+        return e
+      end
+      raise ""
+    end
+  end
+end
diff --git a/src/db/statement.cr b/src/db/statement.cr
index 3eae1f6..b1a8173 100644
--- a/src/db/statement.cr
+++ b/src/db/statement.cr
@@ -65,7 +65,7 @@ module DB
 
     # See `QueryMethods#exec`
     def exec(*t_args, args : Array? = nil) : DB::ExecResult
-      perform_exec_and_release(args || t_args)
+      perform_exec_and_release(EnumerableConcat.build(t_args, args))
     end
 
     # See `QueryMethods#query`
@@ -75,7 +75,7 @@ module DB
 
     # See `QueryMethods#query`
     def query(*t_args, args : Array? = nil) : DB::ResultSet
-      perform_query_with_rescue(args || t_args)
+      perform_query_with_rescue(EnumerableConcat.build(t_args, args))
     end
 
     private def perform_exec_and_release(args : Enumerable) : ExecResult