重置序列

Question

我已阅读了几篇关于TSQL Identity Bug的帖子，并且一直在使用SEQUENCE。但是，我很想知道重置表中SEQUENCE值的ID。举个例子：

CREATE SEQUENCE Inc
    AS INT
    START WITH 1
    INCREMENT BY 1
    CYCLE 
    CACHE 

-- Quick ability to redo everything if needed:
-- DROP SEQUENCE Inc

-- Our table grabs the next sequence for our ID field:
CREATE TABLE SequenceID(
    NewIDField INT DEFAULT NEXT VALUE FOR Inc,
    Name VARCHAR(100)
)

INSERT INTO SequenceID (Name)
VALUES ('John')
    , ('Tiffany')
    , ('Bob')
    , ('Jessica')

SELECT *
FROM SequenceID

-- We remove Bob:
DELETE FROM SequenceID
WHERE NewIDField = 3

-- ID value 3 is gone; it moves from 1 to 2 to 4
SELECT *
FROM SequenceID

INSERT INTO SequenceID (Name)
VALUES ('David')
    , ('Rosa')
    , ('Samuel')

-- ID 3 doesn't exist because the SEQUENCE grabs the next value from 4
SELECT *
FROM SequenceID

-- Let's just reset our ID
;WITH ResetIt AS(
    SELECT ROW_NUMBER() OVER (ORDER BY NewIDField) AS ID
        , NewIDField AS ExistingID
        , Name
    FROM SequenceID
)
UPDATE SequenceID
SET NewIDField = ResetIt.ID
FROM ResetIt
WHERE SequenceID.NewIDField = ResetIt.ExistingID

-- Yay!
SELECT *
FROM SequenceID

INSERT INTO SequenceID (Name)
VALUES ('Sarah')

-- Oh Sarah, tsk tsk.
SELECT *
FROM SequenceID

DROP TABLE SequenceID

有没有办法使用SEQUENCE自动执行此操作，我们可以确定最后一个值并从那里开始（类似于RESEED），就像使用IDENTITY一样，如果我们删除一个值，我们仍然必须{{ 1}}，见：

RESEED

Answer 1

执行更新后，您必须运行一些动态SQL，因为ALTER SEQUENCE只接受RESTART WITH子句的常量：

DECLARE @resetSQL nvarchar(255) = 'ALTER SEQUENCE Inc RESTART WITH ' + (SELECT CAST(MAX(NewIDField)+1 as nvarchar(10)) FROM SequenceID);

exec sp_executesql @resetSQL;