Remove Identity from a column in a table

We have a 5GB table (nearly 500 million rows) and we want to remove the identity property on one of the column, but when we try to do this through SSMS - it times out.

Can this be done through T-SQL?

Answers


You cannot remove an IDENTITY specification once set.

To remove the entire column:

ALTER TABLE yourTable
DROP COLUMN yourCOlumn;

Information about ALTER TABLE here

If you need to keep the data, but remove the IDENTITY column, you will need to:

  • Create a new column
  • Transfer the data from the existing IDENTITY column to the new column
  • Drop the existing IDENTITY column.
  • Rename the new column to the original column name

If you want to do this without adding and populating a new column, without reordering the columns, and with almost no downtime because no data is changing on the table, let's do some magic with partitioning functionality (but since no partitions are used you don't need Enterprise edition):

  1. Remove all foreign keys that point to this table
  2. Script the table to be created; rename everything e.g. 'MyTable2', 'MyIndex2', etc. Remove the IDENTITY specification.
  3. You should now have two "identical"-ish tables, one full, the other empty with no IDENTITY.
  4. Run ALTER TABLE [Original] SWITCH TO [Original2]
  5. Now your original table will be empty and the new one will have the data. You have switched the metadata for the two tables (instant).
  6. Drop the original (now-empty table), exec sys.sp_rename to rename the various schema objects back to the original names, and then you can recreate your foreign keys.

For example, given:

CREATE TABLE Original
(
  Id INT IDENTITY PRIMARY KEY
, Value NVARCHAR(300)
);
CREATE NONCLUSTERED INDEX IX_Original_Value ON Original (Value);

INSERT INTO Original
SELECT 'abcd'
UNION ALL 
SELECT 'defg';

You can do the following:

--create new table with no IDENTITY
CREATE TABLE Original2
(
  Id INT PRIMARY KEY
, Value NVARCHAR(300)
);
CREATE NONCLUSTERED INDEX IX_Original_Value2 ON Original2 (Value);

--data before switch
SELECT 'Original', *
FROM Original
UNION ALL
SELECT 'Original2', *
FROM Original2;

ALTER TABLE Original SWITCH TO Original2;

--data after switch
SELECT 'Original', *
FROM Original
UNION ALL
SELECT 'Original2', *
FROM Original2;

--clean up
DROP TABLE Original;
EXEC sys.sp_rename 'Original2.IX_Original_Value2', 'IX_Original_Value', 'INDEX';
EXEC sys.sp_rename 'Original2', 'Original', 'OBJECT';


UPDATE Original
SET Id = Id + 1;

SELECT *
FROM Original;

This gets messy with foreign and primary key constraints, so here's some scripts to help you on your way:

First, create a duplicate column with a temporary name:

alter table yourTable add tempId int NOT NULL default -1;
update yourTable set tempId = id;

Next, get the name of your primary key constraint:

SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE TABLE_NAME = 'yourTable';

Now try drop the primary key constraint for your column:

ALTER TABLE yourTable DROP CONSTRAINT PK_yourTable_id;

If you have foreign keys, it will fail, so if so drop the foreign key constraints. KEEP TRACK OF WHICH TABLES YOU RUN THIS FOR SO YOU CAN ADD THE CONSTRAINTS BACK IN LATER!!!

SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE TABLE_NAME = 'otherTable';
alter table otherTable drop constraint fk_otherTable_yourTable;
commit;
..

Once all of your foreign key constraints have been removed, you'll be able to remove the PK constraint, drop that column, rename your temp column, and add the PK constraint to that column:

ALTER TABLE yourTable DROP CONSTRAINT PK_yourTable_id;
alter table yourTable drop column id;
EXEC sp_rename 'yourTable.tempId', 'id', 'COLUMN';
ALTER TABLE yourTable ADD CONSTRAINT PK_yourTable_id PRIMARY KEY (id) 
commit;

Finally, add the FK constraints back in:

alter table otherTable add constraint fk_otherTable_yourTable foreign key (yourTable_id) references yourTable(id);
..

El Fin!


I just had this same problem. 4 statements in SSMS instead of using the GUI and it was very fast.

  • Make a new column

    alter table users add newusernum int;

  • Copy values over

    update users set newusernum=usernum;

  • Drop the old column

    alter table users drop column usernum;

  • Rename the new column to the old column name

    EXEC sp_RENAME 'users.newusernum' , 'usernum', 'COLUMN';


Following script removes Identity field for a column named 'Id'

Hope it helps.

BEGIN TRAN
BEGIN TRY
    EXEC sp_rename '[SomeTable].[Id]', 'OldId';

    ALTER TABLE [SomeTable] ADD Id int NULL

    EXEC ('UPDATE [SomeTable] SET Id = OldId')

    ALTER TABLE [SomeTable] NOCHECK CONSTRAINT ALL

    ALTER TABLE [SomeTable] DROP CONSTRAINT [PK_constraintName];
    ALTER TABLE [SomeTable] DROP COLUMN OldId
    ALTER TABLE [SomeTable] ALTER COLUMN [Id] INTEGER NOT NULL
    ALTER TABLE [SomeTable] ADD CONSTRAINT PK_JobInfo PRIMARY KEY (Id)

    ALTER TABLE [SomeTable] CHECK CONSTRAINT ALL

    COMMIT TRAN
END TRY
BEGIN CATCH
    ROLLBACK TRAN   
    SELECT ERROR_MESSAGE ()
END CATCH

Bellow code working as fine, when we don't know identity column name.

and want to copy data into new temp table like Invoice_DELETED. and next time we using: insert into Invoice_DELETED select * from Invoice where ...

SELECT t1.*
INTO Invoice_DELETED
FROM Invoice t1
LEFT JOIN Invoice ON 1 = 0
--WHERE t1.InvoiceID = @InvoiceID

special thanks to 'Andriy M'

for more explanation see: https://dba.stackexchange.com/a/138345/101038


ALTER TABLE tablename add newcolumn int
update tablename set newcolumn=existingcolumnname
ALTER TABLE tablename DROP COLUMN existingcolumnname;
EXEC sp_RENAME 'tablename.oldcolumn' , 'newcolumnname', 'COLUMN'

However above code works only if no primary-foreign key relation


Just for someone who have the same problem I did. If you just want to make some insert just once you can do something like this.

Lets suppose you have a table with two columns

ID Identity (1,1) | Name Varchar

and want to insert a row with the ID = 4. So you Reseed it to 3 so the next one is 4

DBCC CHECKIDENT([YourTable], RESEED, 3)

Make the Insert

INSERT  INTO [YourTable]
        ( Name )
VALUES  ( 'Client' )

And get your seed back to the highest ID, lets suppose is 15

DBCC CHECKIDENT([YourTable], RESEED, 15)

Done!


I had the same requirement, and you could try this way, which I personally recommend you, please manually design your table and generate the script, and what I did below was renaming the old table and also its constraint for backup.

/* To prevent any potential data loss issues, you should review this script in detail before running it outside the context of the database designer.*/
BEGIN TRANSACTION

SET QUOTED_IDENTIFIER ON
SET ARITHABORT ON
SET NUMERIC_ROUNDABORT OFF
SET CONCAT_NULL_YIELDS_NULL ON
SET ANSI_NULLS ON
SET ANSI_PADDING ON
SET ANSI_WARNINGS ON
COMMIT
BEGIN TRANSACTION
GO
ALTER TABLE dbo.SI_Provider_Profile
    DROP CONSTRAINT DF_SI_Provider_Profile_SIdtDateTimeStamp
GO
ALTER TABLE dbo.SI_Provider_Profile
    DROP CONSTRAINT DF_SI_Provider_Profile_SIbHotelPreLoaded
GO
CREATE TABLE dbo.Tmp_SI_Provider_Profile
    (
    SI_lProvider_Profile_ID int NOT NULL,
    SI_lSerko_Integrator_Token_ID int NOT NULL,
    SI_sSerko_Integrator_Provider varchar(50) NOT NULL,
    SI_sSerko_Integrator_Profile varchar(50) NOT NULL,
    SI_dtDate_Time_Stamp datetime NOT NULL,
    SI_lProvider_ID int NULL,
    SI_sDisplay_Name varchar(10) NULL,
    SI_lPurchased_From int NULL,
    SI_sProvider_UniqueID varchar(255) NULL,
    SI_bHotel_Pre_Loaded bit NOT NULL,
    SI_sSiteName varchar(255) NULL
    )  ON [PRIMARY]
GO
ALTER TABLE dbo.Tmp_SI_Provider_Profile SET (LOCK_ESCALATION = TABLE)
GO
ALTER TABLE dbo.Tmp_SI_Provider_Profile ADD CONSTRAINT
    DF_SI_Provider_Profile_SIdtDateTimeStamp DEFAULT (getdate()) FOR SI_dtDate_Time_Stamp
GO
ALTER TABLE dbo.Tmp_SI_Provider_Profile ADD CONSTRAINT
    DF_SI_Provider_Profile_SIbHotelPreLoaded DEFAULT ((0)) FOR SI_bHotel_Pre_Loaded
GO
IF EXISTS(SELECT * FROM dbo.SI_Provider_Profile)
        EXEC('INSERT INTO dbo.Tmp_SI_Provider_Profile (SI_lProvider_Profile_ID, SI_lSerko_Integrator_Token_ID, SI_sSerko_Integrator_Provider, SI_sSerko_Integrator_Profile, SI_dtDate_Time_Stamp, SI_lProvider_ID, SI_sDisplay_Name, SI_lPurchased_From, SI_sProvider_UniqueID, SI_bHotel_Pre_Loaded, SI_sSiteName)
        SELECT SI_lProvider_Profile_ID, SI_lSerko_Integrator_Token_ID, SI_sSerko_Integrator_Provider, SI_sSerko_Integrator_Profile, SI_dtDate_Time_Stamp, SI_lProvider_ID, SI_sDisplay_Name, SI_lPurchased_From, SI_sProvider_UniqueID, SI_bHotel_Pre_Loaded, SI_sSiteName FROM dbo.SI_Provider_Profile WITH (HOLDLOCK TABLOCKX)')
GO

-- Rename the primary key constraint or unique key In SQL Server constraints such as primary keys or foreign keys are objects in their own right, even though they are dependent upon the "containing" table.
EXEC sp_rename 'dbo.SI_Provider_Profile.PK_SI_Provider_Profile', 'PK_SI_Provider_Profile_Old';
GO
-- backup old table in case of 
EXECUTE sp_rename N'dbo.SI_Provider_Profile', N'SI_Provider_Profile_Old', 'OBJECT'
GO

EXECUTE sp_rename N'dbo.Tmp_SI_Provider_Profile', N'SI_Provider_Profile', 'OBJECT'
GO

ALTER TABLE dbo.SI_Provider_Profile ADD CONSTRAINT
    PK_SI_Provider_Profile PRIMARY KEY NONCLUSTERED 
    (
    SI_lProvider_Profile_ID
    ) WITH( PAD_INDEX = OFF, FILLFACTOR = 90, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

GO
COMMIT TRANSACTION

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