Update med värde från annan tabell

SqlServer 2005

Vill köra en UPDATE på Table1, och minska dess Quantity värde med det värdet som Table2.QuantityMinusValue har, om den har något för det Table1.Id:t.

CREATE TABLE [Table1] (
	[Id] [int] IDENTITY (1, 1) NOT FOR REPLICATION  NOT NULL ,
	[Quantity] [int] NOT NULL ,
	CONSTRAINT [PK_Table1] PRIMARY KEY  CLUSTERED 
	(
		[Id]
	)  ON [PRIMARY] 
) ON [PRIMARY]
GO

CREATE TABLE [Table2] (
	[Id] [int] IDENTITY (1, 1) NOT FOR REPLICATION  NOT NULL ,
	[Table1Id] [int] NOT NULL ,
	[QuantityMinusValue] [int] NOT NULL ,
	CONSTRAINT [PK_Table2] PRIMARY KEY  CLUSTERED 
	(
		[Id]
	)  ON [PRIMARY] 
) ON [PRIMARY]
GO

INSERT INTO dbo.[Table1](Quantity) VALUES(3);
INSERT INTO dbo.[Table1](Quantity) VALUES(25);
INSERT INTO dbo.[Table1](Quantity) VALUES(18);
INSERT INTO dbo.[Table1](Quantity) VALUES(9);

INSERT INTO dbo.[Table2](Table1Id, QuantityMinusValue) VALUES(2, 13);
INSERT INTO dbo.[Table2](Table1Id, QuantityMinusValue) VALUES(4, 8);

SELECT * FROM dbo.[Table1]
SELECT * FROM dbo.[Table2]