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sql-serverauto-incrementdelete-row
jumbojs
jumbojs

Reputation: 4868

Reset AutoIncrement in SQL Server after Delete

I've deleted some records from a table in a SQL Server database.

The IDs in the table look like this:

99 100 101 1200 1201...

I want to delete the later records (IDs >1200), then I want to reset the auto increment so the next autogenerated ID will be 102. So my records are sequential, Is there a way to do this in SQL Server?

Upvotes: 342

Views: 574556

Answers (14)

Michael Rodby
Michael Rodby

Reputation: 376

Several answers recommend using a statement something like this:

DBCC CHECKIDENT (mytable, RESEED, 0)

But the OP said "deleted some records", which may not be all of them, so a value of 0 is not always the right one. Another answer suggested automatically finding the maximum current value and reseeding to that one, but that runs into trouble if there are no records in the table, and thus max() will return NULL. A comment suggested using simply

DBCC CHECKIDENT (mytable)

to reset the value, but another comment correctly stated that this only increases the value to the maximum already in the table; this will not reduce the value if it is already higher than the maximum in the table, which is what the OP wanted to do.

A better solution combines these ideas. The first CHECKIDENT resets the value to 0, and the second resets it to the highest value currently in the table, in case there are records in the table:

DBCC CHECKIDENT (mytable, RESEED, 0)
DBCC CHECKIDENT (mytable, RESEED)

As multiple comments have indicated, make sure there are no foreign keys in other tables pointing to the deleted records. Otherwise those foreign keys will point at records you create after reseeding the table, which is almost certainly not what you had in mind.

Upvotes: 8

Robert Wagner
Robert Wagner

Reputation: 17793

Issue the following command to reseed mytable to start at ID 1:

DBCC CHECKIDENT ('mytable', RESEED, 0);

Read about it in the Books on Line (BOL, SQL help). Also be careful that you don't have records higher than the seed you are setting.

Upvotes: 584

Fathah Rehman P
Fathah Rehman P

Reputation: 8761

DBCC CHECKIDENT('databasename.dbo.tablename', RESEED, number)

if number = 0 then in the next insert the auto increment field will contain value 1

if number = 101 then in the next insert the auto increment field will contain value 102

Additional info

Before giving auto increment number in above query, you have to make sure your existing table's auto increment column contain values less that number.

To get the maximum value of a column(column_name) from a table(table1), you can use following query

SELECT MAX(column_name) FROM table1

Upvotes: 124

Hossein Mehrandish
Hossein Mehrandish

Reputation: 81

I think the best one is:

declare @max int  
select @max = isnull(max(key),1) from table  
dbcc checkident(table,reseed,@max)

Upvotes: 0

Joseph Ali
Joseph Ali

Reputation: 355

I know this is an old question. However, I was looking for a similar solution for MySQL and this question showed up.

for those who are looking for MySQL solution, you need to run this query:

// important!!! You cannot reset the counter to a value less than or equal to the value that is currently in use. For both InnoDB and MyISAM, if the value is less than or equal to the maximum value currently in the AUTO_INCREMENT column, the value is reset to the current maximum AUTO_INCREMENT column value plus one.
   
ALTER TABLE <your-table-name> AUTO_INCREMENT = 100

documentation

Upvotes: 0

statler
statler

Reputation: 1381

To reset every key in the database to autoincrement from the max of the last highest key:

Exec sp_MSforeachtable 'DBCC CHECKIDENT(''?'', RESEED, 0)'

Exec sp_MSforeachtable 'DBCC CHECKIDENT(''?'', RESEED)'

Upvotes: 1

Yashaswini Bhat
Yashaswini Bhat

Reputation: 81

If you just want to reset the primary key/sequence to start with a sequence you want in a SQL server, here's the solution -

IDs:

99 100 101 1200 1201...

  1. Drop rows with IDs >= 1200. (Be careful if you have foreign key constraints tied to these which has to be dealed with or deleted too to be able to delete this.)
  2. Now you want to make sure you know the MAX ID to be sure:

declare @max_id as int = (SELECT MAX(your_column_name) FROM your_table)+1;

(Note: +1 to start the ID sequence after max value)

  1. Restart your sequence:

exec('alter sequence your_column_name restart with ' + @max_id);

(Note: Space after with is necessary) Now new records will start with 102 as the ID.

Upvotes: 0

Victor Resnov
Victor Resnov

Reputation: 292

What about this?

ALTER TABLE `table_name`
  MODIFY `id` int(12) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=0;

This is a quick and simple way to change the auto increment to 0 or whatever number you want. I figured this out by exporting a database and reading the code myself.

You can also write it like this to make it a single-line solution:

ALTER TABLE `table_name` MODIFY `id` int(12) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=0;

Upvotes: 1

Alexander Schmidt
Alexander Schmidt

Reputation: 5743

I want to add this answer because the DBCC CHECKIDENT-approach will product problems when you use schemas for tables. Use this to be sure:

DECLARE @Table AS NVARCHAR(500) = 'myschema.mytable';
DBCC CHECKIDENT (@Table, RESEED, 0);

If you want to check the success of the operation, use

SELECT IDENT_CURRENT(@Table);

which should output 0 in the example above.

Upvotes: 4

tinonetic
tinonetic

Reputation: 8044

Based on the accepted answer, for those who encountered a similar issue, with full schema qualification:

([MyDataBase].[MySchemaName].[MyTable])... results in an error, you need to be in the context of that DB

That is, the following will throw an error:

DBCC CHECKIDENT ([MyDataBase].[MySchemaName].[MyTable], RESEED, 0)

Enclose the fully-qualified table name with single quotes instead:

DBCC CHECKIDENT ('[MyDataBase].[MySchemaName].[MyTable]', RESEED, 0)

Upvotes: 6

jumbojs
jumbojs

Reputation: 4868

I figured it out. It's:

 DBCC CHECKIDENT ('tablename', RESEED, newseed)

Upvotes: 11

BMG
BMG

Reputation: 489

Delete and Reseed all the tables in a database.

    USE [DatabaseName]
    EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"       -- Disable All the constraints
    EXEC sp_MSForEachTable "DELETE FROM ?"    -- Delete All the Table data
    Exec sp_MSforeachtable 'DBCC CHECKIDENT(''?'', RESEED, 0)' -- Reseed All the table to 0
    Exec sp_msforeachtable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all"  -- Enable All  the constraints back

-- You may ignore the errors that shows the table without Auto increment field.

Upvotes: 8

user423430
user423430

Reputation: 3714

semi idiot-proof:

declare @max int;  
select @max = max(key) from table;  
dbcc checkident(table,reseed,@max)

http://sqlserverplanet.com/tsql/using-dbcc-checkident-to-reseed-a-table-after-delete

Upvotes: 52

HLGEM
HLGEM

Reputation: 96650

You do not want to do this in general. Reseed can create data integrity problems. It is really only for use on development systems where you are wiping out all test data and starting over. It should not be used on a production system in case all related records have not been deleted (not every table that should be in a foreign key relationship is!). You can create a mess doing this and especially if you mean to do it on a regular basis after every delete. It is a bad idea to worry about gaps in you identity field values.

Upvotes: 1

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