SQLServer中NEWID()函数用于生成一个唯一的标识符的方法实践

NEWID()

uniqueidentifier

NEWID() 遵从 RFC4122。

CREATE TABLE Employees (
    EmployeeID UNIQUEIDENTIFIER CONSTRAINT PK_Employees_EmployeeID PRIMARY KEY CONSTRAINT df_Employees_newid DEFAULT NEWID(),
    EmployeeName NVARCHAR(100)
);

-- 插入新记录时，EmployeeID将自动由NEWID()生成
INSERT INTO Employees (EmployeeName) VALUES ('John Doe'),(N'主键约束'),(N'默认值约束');

-- 查看插入的记录
SELECT * FROM Employees;

EmployeeID                           EmployeeName
------------------------------------ -------------------------------------------------
A622FFE4-10B2-46BC-BAC6-4505495845D2 John Doe
75D6A200-0A8A-4247-B446-E7CB79A59EA0 默认值约束
4BAFD083-E206-46FC-A8A8-F5FE3150871B 主键约束

(3 行受影响)

-- Creating a local variable with DECLARE/SET syntax.  
DECLARE @myid uniqueidentifier  
SET @myid = NEWID()  
PRINT 'Value of @myid is: '+ CONVERT(varchar(255), @myid)

DECLARE @mynewid uniqueidentifier ;  
SET @mynewid = 'A9CBD0DB-F4A6-4E55-92C6-4C5116A1DD9E';  
SELECT @mynewid AS sysguid;  
GO 

sysguid
------------------------------------
A9CBD0DB-F4A6-4E55-92C6-4C5116A1DD9E

(1 行受影响)

SELECT TOP 1 ProductID, Name, ProductNumber
FROM Production.Product
ORDER BY NEWID()
GO

ProductID   Name                                               ProductNumber
----------- -------------------------------------------------- -------------------------
824         ML Mountain Rear Wheel                             RW-M762

(1 行受影响)

-- 第二次执行，返回结果和前一次可能不同，则是ORDER BY NEWID()随机排序查询的作用
ProductID   Name                                               ProductNumber
----------- -------------------------------------------------- -------------------------
842         Touring-Panniers, Large                            PA-T100

(1 行受影响)