diff --git a/src/Carbunql/Building/SelectClauseExtension.cs b/src/Carbunql/Building/SelectClauseExtension.cs
index 4be2bb6d..152c99b9 100644
--- a/src/Carbunql/Building/SelectClauseExtension.cs
+++ b/src/Carbunql/Building/SelectClauseExtension.cs
@@ -182,4 +182,10 @@ public static void Order(this SelectQuery source, string table, string column)
 		source.OrderClause ??= new();
 		source.OrderClause.Add(item);
 	}
+
+	public static void Window(this SelectQuery source, NamedWindowDefinition namedWindow)
+	{
+		source.WindowClause ??= new();
+		source.WindowClause.Add(namedWindow);
+	}
 }
\ No newline at end of file
diff --git a/src/Carbunql/Building/WindowFunctionExtension.cs b/src/Carbunql/Building/WindowFunctionExtension.cs
index 91b5732c..a9954df6 100644
--- a/src/Carbunql/Building/WindowFunctionExtension.cs
+++ b/src/Carbunql/Building/WindowFunctionExtension.cs
@@ -1,34 +1,121 @@
 using Carbunql.Clauses;
+using Carbunql.Values;
 
 namespace Carbunql.Building;
 
 public static class WindowFunctionExtension
 {
-    public static void AddPartition(this OverClause source, ValueBase partition)
-    {
-        source.WindowDefinition ??= new();
-		source.WindowDefinition.PartitionBy ??= new();
-        source.WindowDefinition.PartitionBy.Add(partition);
-    }
+	public static void Partition(this OverClause source, ValueBase partition)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Partition(partition);
+	}
+
+	public static void Partition(this OverClause source, Func<ValueBase> partitionbuilder)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Partition(partitionbuilder());
+	}
+
+	public static void Partition(this OverClause source, SelectableItem order)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Partition(order.Value);
+	}
+
+	public static void Order(this OverClause source, ColumnValue order)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Order(order.ToSortable());
+	}
+
+	public static void Order(this OverClause source, SortableItem order)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Order(order);
+	}
+
+	public static void Order(this OverClause source, Func<SortableItem> orderbuilder)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Order(orderbuilder());
+	}
+
+	public static void Partition(this WindowDefinition source, ValueBase partition)
+	{
+		source.PartitionBy ??= new();
+		source.PartitionBy.Add(partition);
+	}
+
+	public static void Partition(this WindowDefinition source, Func<ValueBase> partitionbuilder)
+	{
+		source.PartitionBy ??= new();
+		source.PartitionBy.Add(partitionbuilder());
+	}
+
+	public static void Partition(this WindowDefinition source, SelectableItem order)
+	{
+		source.PartitionBy ??= new();
+		source.PartitionBy.Add(order.Value);
+	}
+
+	public static void Order(this WindowDefinition source, ColumnValue order)
+	{
+		source.OrderBy ??= new();
+		source.OrderBy.Add(order.ToSortable());
+	}
+
+	public static void Order(this WindowDefinition source, SortableItem order)
+	{
+		source.OrderBy ??= new();
+		source.OrderBy.Add(order);
+	}
+
+	public static void Order(this WindowDefinition source, Func<SortableItem> orderbuilder)
+	{
+		source.OrderBy ??= new();
+		source.OrderBy.Add(orderbuilder());
+	}
+
+	public static void Partition(this NamedWindowDefinition source, ValueBase partition)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Partition(partition);
+	}
+
+	public static void Partition(this NamedWindowDefinition source, Func<ValueBase> partitionbuilder)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Partition(partitionbuilder());
+	}
+
+	public static void Partition(this NamedWindowDefinition source, SelectableItem order)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Partition(order.Value);
+	}
+
+	public static void Order(this NamedWindowDefinition source, ColumnValue order)
+	{
+		source.WindowDefinition ??= new();
+		source.WindowDefinition.Order(order.ToSortable());
+	}
 
-    public static void AddPartition(this OverClause source, Func<ValueBase> partitionbuilder)
-    {
+	public static void Order(this NamedWindowDefinition source, SelectableItem order)
+	{
 		source.WindowDefinition ??= new();
-		source.WindowDefinition.PartitionBy ??= new();
-        source.WindowDefinition.PartitionBy.Add(partitionbuilder());
-    }
+		source.WindowDefinition.Order(order.Value.ToSortable());
+	}
 
-    public static void AddOrder(this OverClause source, SortableItem order)
-    {
+	public static void Order(this NamedWindowDefinition source, SortableItem order)
+	{
 		source.WindowDefinition ??= new();
-		source.WindowDefinition.OrderBy ??= new();
-        source.WindowDefinition.OrderBy.Add(order);
-    }
+		source.WindowDefinition.Order(order);
+	}
 
-    public static void AddOrder(this OverClause source, Func<SortableItem> orderbuilder)
-    {
+	public static void Order(this NamedWindowDefinition source, Func<SortableItem> orderbuilder)
+	{
 		source.WindowDefinition ??= new();
-		source.WindowDefinition.OrderBy ??= new();
-        source.WindowDefinition.OrderBy.Add(orderbuilder());
-    }
+		source.WindowDefinition.Order(orderbuilder());
+	}
 }
diff --git a/src/Carbunql/Clauses/NamedWindowDefinition.cs b/src/Carbunql/Clauses/NamedWindowDefinition.cs
index d4c3be0f..52c627b5 100644
--- a/src/Carbunql/Clauses/NamedWindowDefinition.cs
+++ b/src/Carbunql/Clauses/NamedWindowDefinition.cs
@@ -12,6 +12,12 @@ public NamedWindowDefinition()
 		WindowDefinition = null!;
 	}
 
+	public NamedWindowDefinition(string alias)
+	{
+		Alias = alias;
+		WindowDefinition = null!;
+	}
+
 	public NamedWindowDefinition(string alias, WindowDefinition definition)
 	{
 		Alias = alias;
diff --git a/src/Carbunql/Clauses/OverClause.cs b/src/Carbunql/Clauses/OverClause.cs
index 60850264..77fe02dd 100644
--- a/src/Carbunql/Clauses/OverClause.cs
+++ b/src/Carbunql/Clauses/OverClause.cs
@@ -16,6 +16,11 @@ public OverClause(WindowDefinition definition)
 		WindowDefinition = definition;
 	}
 
+	public OverClause(NamedWindowDefinition definition)
+	{
+		WindowDefinition = new WindowDefinition(definition.Alias);
+	}
+
 	public WindowDefinition WindowDefinition { get; set; }
 
 	public IEnumerable<CommonTable> GetCommonTables()
diff --git a/test/Carbunql.Building.Test/FunctionTest.cs b/test/Carbunql.Building.Test/FunctionTest.cs
index 4e3cc101..528b8e02 100644
--- a/test/Carbunql.Building.Test/FunctionTest.cs
+++ b/test/Carbunql.Building.Test/FunctionTest.cs
@@ -48,8 +48,8 @@ public void RowNumberTest()
 		sq.Select(() =>
 		{
 			var wf = new OverClause();
-			wf.AddPartition(new ColumnValue(a, "parent_id"));
-			wf.AddOrder(new ColumnValue(a, "id").ToSortable());
+			wf.Partition(new ColumnValue(a, "parent_id"));
+			wf.Order(new ColumnValue(a, "id").ToSortable());
 			return new FunctionValue("row_number", wf);
 		}).As("val");
 
diff --git a/test/Carbunql.Building.Test/SerializeTest.ValueBase.cs b/test/Carbunql.Building.Test/SerializeTest.ValueBase.cs
index b1bde723..36c42f05 100644
--- a/test/Carbunql.Building.Test/SerializeTest.ValueBase.cs
+++ b/test/Carbunql.Building.Test/SerializeTest.ValueBase.cs
@@ -231,8 +231,8 @@ public void QueryContainer()
 	public void WindowFunction()
 	{
 		var win = new OverClause();
-		win.AddPartition(new ColumnValue("shop_id"));
-		win.AddOrder(new Clauses.SortableItem(new ColumnValue("order_id")));
+		win.Partition(new ColumnValue("shop_id"));
+		win.Order(new SortableItem(new ColumnValue("order_id")));
 
 		var sq = new FunctionValue("row_number", win);
 
diff --git a/test/Carbunql.Building.Test/WindowTest.cs b/test/Carbunql.Building.Test/WindowTest.cs
new file mode 100644
index 00000000..4be9fe47
--- /dev/null
+++ b/test/Carbunql.Building.Test/WindowTest.cs
@@ -0,0 +1,111 @@
+using Carbunql.Clauses;
+using Carbunql.Values;
+using Xunit.Abstractions;
+
+namespace Carbunql.Building.Test;
+
+public class WindowTest
+{
+	private readonly QueryCommandMonitor Monitor;
+
+	public WindowTest(ITestOutputHelper output)
+	{
+		Monitor = new QueryCommandMonitor(output);
+	}
+
+	[Fact]
+	public void Default()
+	{
+		var sq = new SelectQuery();
+		var (_, a) = sq.From("table_a").As("a");
+
+		var pc = new PartitionClause
+		{
+			new ColumnValue(a, "name")
+		};
+		var oc = new OrderClause {
+			new ColumnValue(a, "a_id").ToSortable()
+		};
+		var wd = new WindowDefinition(pc, oc);
+		var w1 = new NamedWindowDefinition("w1", wd);
+
+		sq.WindowClause ??= new();
+		sq.WindowClause.Add(w1);
+
+		sq.Select(new FunctionValue("row_number", new OverClause(w1))).As("row_num");
+
+		Monitor.Log(sq);
+
+		var expect = @"SELECT
+    ROW_NUMBER() OVER w1 AS row_num
+FROM
+    table_a AS a
+WINDOW
+    w1 AS (
+        PARTITION BY
+            a.name
+        ORDER BY
+            a.a_id
+    )";
+
+		Assert.Equal(expect, sq.ToText().ToString(), true, true, true);
+	}
+
+	[Fact]
+	public void NamedWindow()
+	{
+		var sq = new SelectQuery();
+		var (_, a) = sq.From("table_a").As("a");
+
+		var w = new NamedWindowDefinition("w1");
+		w.Partition(new ColumnValue(a, "name"));
+		w.Order(new ColumnValue(a, "a_id"));
+
+		sq.Window(w);
+
+		sq.Select(new FunctionValue("row_number", new OverClause(w))).As("row_num");
+
+		Monitor.Log(sq);
+
+		var expect = @"SELECT
+    ROW_NUMBER() OVER w1 AS row_num
+FROM
+    table_a AS a
+WINDOW
+    w1 AS (
+        PARTITION BY
+            a.name
+        ORDER BY
+            a.a_id
+    )";
+
+		Assert.Equal(expect, sq.ToText().ToString(), true, true, true);
+	}
+
+	[Fact]
+	public void Window()
+	{
+		var sq = new SelectQuery();
+		var (_, a) = sq.From("table_a").As("a");
+
+		var w = new WindowDefinition();
+		w.Partition(new ColumnValue(a, "name"));
+		w.Order(new ColumnValue(a, "a_id"));
+
+		sq.Select(new FunctionValue("row_number", new OverClause(w))).As("row_num");
+
+		Monitor.Log(sq);
+
+		var expect = @"SELECT
+    ROW_NUMBER() OVER(
+        PARTITION BY
+            a.name
+        ORDER BY
+            a.a_id
+    ) AS row_num
+FROM
+    table_a AS a";
+
+		Assert.Equal(expect, sq.ToText().ToString(), true, true, true);
+	}
+}
\ No newline at end of file