如何使用SQL Server中的ID連接字符串？

Question

這是我的T-SQL代碼。

CREATE TABLE [dbo].[AspNetUsers] 
(
    [Id]   NVARCHAR (128) NOT NULL, 
    [Email]   NVARCHAR (256) NULL, 
    [PasswordHash] NVARCHAR (MAX) NULL, 
    [UserName]  NVARCHAR (256) NOT NULL, 
    [FirstName]  NVARCHAR(50) NOT NULL DEFAULT /*what goes in here*/, 
    [LastName]  NVARCHAR(50) NOT NULL DEFAULT 'LastName', 

    CONSTRAINT [PK_dbo.AspNetUsers] 
     PRIMARY KEY CLUSTERED ([Id] ASC) 
); 
GO 

CREATE UNIQUE NONCLUSTERED INDEX [UserNameIndex] 
    ON [dbo].[AspNetUsers]([UserName] ASC); 

我想FirstName和LastName將不允許作爲空，但我不斷收到一個錯誤說，我要麼添加默認或任我應該讓他們有空值（我不想做完全）。所以我想我會添加默認值。我想採用Id並將其與連字和LastName連接起來。

例如，如果我的Id是345，我希望我默認值FirstName和LastName分別爲345FirstName和345LastName（的nvarchar的類型）。

那麼我該如何做到這一點？

Answer 1

你可以讓這個字段爲空的和更新後添加，INSERT觸發器：

CREATE TABLE [dbo].[AspNetUsers] (
    [Id]     NVARCHAR (128) NOT NULL, 
    [Email]    NVARCHAR (256) NULL, 
    [PasswordHash]   NVARCHAR (MAX) NULL, 
    [UserName]    NVARCHAR (256) NOT NULL, 
    [FirstName] NVARCHAR(50) NULL, 
    [LastName] NVARCHAR(50) NULL, 
    CONSTRAINT [PK_dbo.AspNetUsers] PRIMARY KEY CLUSTERED ([Id] ASC) 
); 


GO 
CREATE UNIQUE NONCLUSTERED INDEX [UserNameIndex] 
    ON [dbo].[AspNetUsers]([UserName] ASC); 
GO 

CREATE TRIGGER [UserNameTrigger] 
ON [dbo].[AspNetUsers] 
AFTER INSERT, UPDATE 
AS 
    UPDATE anu 
    SET [FirstName] = ISNULL(i.[FirstName],i.Id + 'FirstName'), 
     [LastName] = ISNULL(i.[LastName],i.Id + 'LastName') 
    FROM [dbo].[AspNetUsers] anu 
    INNER JOIN inserted i 
     ON i.[Id] = anu.Id 
GO 

所以，如果你運行此查詢：

INSERT INTO [dbo].[AspNetUsers] 
VALUES 
(NEWID(),'example1@example.com','qwerty','username1',NULL,NULL), 
(NEWID(),'example2@example.com','qwerty','username2','John',NULL), 
(NEWID(),'example3@example.com','qwerty','username3',NULL,'Smith'), 
(NEWID(),'example4@example.com','qwerty','username4','Jason','Anderson') 
GO 

SELECT [Id] 
     ,[Email] 
     ,[PasswordHash] 
     ,[UserName] 
     ,[FirstName] 
     ,[LastName] 
    FROM [dbo].[AspNetUsers] 
GO 

您將獲得：

Id          Email     PasswordHash UserName FirstName          LastName 
07AA1C80-7386-4E48-9556-9D81E2FBFCB0 example2@example.com qwerty   username2 John           07AA1C80-7386-4E48-9556-9D81E2FBFCB0LastName 
6310E4E6-ADDB-4F50-9D1E-5C756059DB40 example1@example.com qwerty   username1 6310E4E6-ADDB-4F50-9D1E-5C756059DB40FirstName 6310E4E6-ADDB-4F50-9D1E-5C756059DB40LastName 
6F539B99-2B4C-440E-A96A-8F5D54A9B758 example3@example.com qwerty   username3 6F539B99-2B4C-440E-A96A-8F5D54A9B758FirstName Smith 
9665747B-A216-46CC-9BA3-159512AAC80C example4@example.com qwerty   username4 Jason           Anderson 

Answer 2

DEFAULT約束必須是常量，你不能在DEFAULT定義上下文中使用列名。我認爲唯一的方法是使用觸發器（我不確定這是不是過度工程）。看看這個例子：

CREATE TABLE [dbo].[AspNetUsers] (
    [Id]     NVARCHAR (128) NOT NULL, 
    [Email]    NVARCHAR (256) NULL, 
    [PasswordHash]   NVARCHAR (MAX) NULL, 
    [UserName]    NVARCHAR (256) NOT NULL, 
    [FirstName] NVARCHAR(50) NOT NULL, 
    [LastName] NVARCHAR(50) NOT NULL, 
    CONSTRAINT [PK_dbo.AspNetUsers] PRIMARY KEY CLUSTERED ([Id] ASC) 
); 
GO 
CREATE TRIGGER trInsert_AspNetUsers 
ON [dbo].[AspNetUsers] INSTEAD OF INSERT 
AS 
    INSERT [dbo].[AspNetUsers]([Id], [Email], [PasswordHash], [UserName], [FirstName], [LastName]) 
    SELECT [Id], [Email], [PasswordHash], [UserName], COALESCE([FirstName], [Id]+'FirstName'), COALESCE([LastName], [Id]+'LastName') 
    FROM inserted 
GO 

INSERT dbo.AspNetUsers VALUES('1', '2', '3','4',NULL,NULL) 
INSERT dbo.AspNetUsers VALUES('5', '6', '7', '8', 'Paweł', 'Dyl') 
SELECT * FROM dbo.AspNetUsers 

SELECT返回下表：

Id Email PasswordHash UserName FirstName  LastName 
1 2  3   4  1FirstName 1LastName 
5 6  7   8  Paweł   Dyl