将现有的标识列转换为序列

如何解决将现有的标识列转换为序列

现有表：

CREATE TABLE [dbo].[Airlines_Mast]
(
    [ID] [int] IDENTITY(1,1) NOT NULL,[Airlines_ID]  AS ('AS'+right('00000'+CONVERT([varchar],[ID]),(6))) PERSISTED NOT NULL,[Airlines_Name] [nvarchar](100) NOT NULL
)

创建的序列：

CREATE SEQUENCE [Airlines_Mast_SEQ]
AS INTEGER
START WITH 3
INCREMENT BY 1
MINVALUE 1
MAXVALUE 99999; 

现有身份列：

[ID] [int] IDENTITY(1,1) NOT NULL

[ID] [INT] DEFAULT NEXT VALUE FOR [Airlines_Mast_SEQ] PRIMARY KEY

如何将现有标识列转换为使用序列？

解决方法

如果您的原始表具有与新表一样的主键约束，您可以使用 SWITCH 将数据移动到具有相同架构（包括索引）的新表中。 IDENTITY 属性元数据将不会保留。您只需要确保序列 START WTIH 值高于现有 MAX(ID) 值

例如：

CREATE SEQUENCE [Airlines_Mast_SEQ]
    AS INTEGER
    START WITH 3
    INCREMENT BY 1
    MINVALUE 1
    MAXVALUE 99999; 
CREATE TABLE dbo.Airlines_Mast
(
    [ID] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY,[Airlines_ID]  AS ('AS'+right('00000'+CONVERT([varchar],[ID]),(6))) PERSISTED NOT NULL,[Airlines_Name] [nvarchar](100) NOT NULL
);
INSERT INTO dbo.Airlines_Mast (Airlines_Name) VALUES (N'example1');
INSERT INTO dbo.Airlines_Mast (Airlines_Name) VALUES (N'example2');
SELECT * FROM dbo.Airlines_Mast;
GO
SET XACT_ABORT ON;
BEGIN TRY;
    BEGIN TRAN;
    CREATE TABLE [dbo].[Airlines_Mast_Sequence]
    (
        [ID] [int] NOT NULL DEFAULT NEXT VALUE FOR [Airlines_Mast_SEQ] PRIMARY KEY,[Airlines_Name] [nvarchar](100) NOT NULL
    );
    ALTER TABLE dbo.Airlines_Mast
        SWITCH TO dbo.Airlines_Mast_Sequence;
    DROP TABLE dbo.Airlines_Mast;
    EXEC sp_rename N'dbo.Airlines_Mast_Sequence',N'Airlines_Mast';
    COMMIT;
END TRY
BEGIN CATCH
    IF @@TRANCOUNT > 0 ROLLBACK;
    THROW;
END CATCH;
GO

INSERT INTO dbo.Airlines_Mast (Airlines_Name) VALUES (N'example3');
SELECT * FROM dbo.Airlines_Mast;

结果：

+----+-------------+---------------+
| ID | Airlines_ID | Airlines_Name |
+----+-------------+---------------+
|  1 | AS000001    | example1      |
|  2 | AS000002    | example2      |
+----+-------------+---------------+

+----+-------------+---------------+
| ID | Airlines_ID | Airlines_Name |
+----+-------------+---------------+
|  1 | AS000001    | example1      |
|  2 | AS000002    | example2      |
|  3 | AS000003    | example3      |
+----+-------------+---------------+