更新标识列中的值

Question

如何覆盖MSSQL中的标识列？我试过了 :

    SET IDENTITY_INSERT GeoCountry ON
    UPDATE GeoCountry SET CountryID = 18 WHERE CountryID = 250

但是我回来了

    SET IDENTITY_INSERT GeoCountry ON
    UPDATE GeoCountry SET CountryID = 18 WHERE CountryID = 250

Answer 1

您正在尝试执行更新,而不是插入新行.

为此,您需要设置identity_insertON 并将要更新的行复制到具有新ID值的新行,然后删除旧行(假设没有FK引用它)

有点像:

set identity_insert GeoCountry on
go

insert into GeoCountry (all columns including IDentity column) 
     select 18, (all columns except IDentity column)
     from GeoCountry where CountryID = 250 

-- Delete will only work if no referencing FK's
delete GeoCountry where CountryID = 250

set identity_insert GeoCountry off
go

[鉴于您正在尝试更新它,这表明它仍在使用中(即通过引用FK)并使事情变得更复杂......]

Answer 2

您无法更新SQL Server中的标识列.您必须删除原始记录,然后使用Identity值插入记录,因为不支持更新标识值.

set Identity_Insert [ColumnName] On插入先前存储在该记录集中的标识和附加信息Identity_Insert [ColumnName] Off

Answer 3

如果您尝试更新标识列,这里有一种可能的方法:

• 在SQL Server Management Studio中,在设计视图中打开表,禁用列上的"标识规范>是标识"
• 执行更新
• 在列上启用"身份规范>身份"

执行a SELECT IDENT_CURRENT('<table name>')以查看它是否返回表中当前存在的最高ID.

Answer 4

您还可以使用 delete into 在一个语句中执行此操作，这具有消除复制/移动行数据的任何错误的好处，例如

set identity_insert [dbo].[MyTableName] on

delete from [dbo].[MyTableName]
output 
<new-id-value-here>,
[deleted].[Col1], 
[deleted].[Col2], 
[deleted].[Col3], 
into 
[dbo].[MyTableName] (
[IdColumnName], 
[Col1], 
[Col2], 
[Col3])
where
[IdColumnName]=<old-id-value-here>

set identity_insert [dbo].[MyTableName] off