SQL 存储过程 - 为什么使用 "OUT"而我只能选择

Question

CREATE PROCEDURE GetImmediateManager
   @employeeID INT,
   @managerID INT OUTPUT
AS
BEGIN
   SELECT @managerID = ManagerID 
   FROM HumanResources.Employee 
   WHERE EmployeeID = @employeeID
END

大家好，我可以知道“OUT”的确切用法吗？它与下面的存储过程有何不同？

CREATE PROCEDURE GetImmediateManager
   @employeeID INT,
   @managerID INT 
AS
BEGIN
   SELECT @managerID = ManagerID 
   FROM HumanResources.Employee 
   WHERE EmployeeID = @employeeID
END

Answer 1

通过以下链接获取答案

( https://technet.microsoft.com/en-us/library/ms187004(v=sql.105).aspx )