他のテーブルの値を使って更新する
UPDATE Salary SET Amount = Amount + ( SELECT (2007 - e.HireFiscalYear) * 1000 FROM Employees AS e WHERE Salary.EmployeeID = e.EmployeeID ) WHERE PayDate = '2008-02-14' AND EXISTS ( SELECT 'X' FROM Employees AS e WHERE Salary.EmployeeID = e.EmployeeID ) ;
「Salary.EmployeeID = e.EmployeeID」が2回出てくるのがしつこい感じがありますね。