I recently added Items to an ID and the the table got messed up in the transfer process so I deleted the Items from the table. Upon reentering the data instead of the ID starting at one it now starts at 332. I would like to have the table start at one instead of 332. I've removed the data from the data so it's clear. How do I reset the ID to one.
Thanks and sorry if this on here somewhere I wasn't sure how to search for this.
In SQL Server:
DBCC CHECKIDENT (myTable, RESEED, 0)
truncate table yourtable --will reseed
Assuming MSSQL:
DBCC CHECKIDENT('MyTable', RESEED, 0) -- One less than next ID to allocate
If you want to remove the data too you can use
TRUNCATE TABLE MyTable
but you cannot use TRUNCATE TABLE on a table referenced by a Foreign Key, or if the table is part of an indexed view, and unlike DELETE MyTable any trigger(s) on the table won't be activated.
Set the starting identity value to 1
DBCC CHECKIDENT (tableName, RESEED, 1)
If you are using MS Access, delete and recreate the table
you need to truncate the table
but to do so it has be empty, and no foreign keys attached to it at all
Related
I have a problem with identity specification when I create a table in SQL Server 2016.
In column Id I set Identity Increment and Identity Seed equal 1.
Next I add new record to new table.
In column Id show up 2 value. Why? Why not 1 value?
Next drop the first record and add new. In column Id show up 3 value. Why? Why not 1 value.
Next I use command ' update nametable set id=1' and receive answer cannot update identity column Id. Why?
This is probably easier to explain with some code:
CREATE TABLE YourTable (ID int IDENTITY(1,1),
SomeCol varchar(5));
INSERT INTO dbo.YourTable (SomeCol)
VALUES('abc'); --Will get ID 1
INSERT INTO dbo.YourTable (SomeCol)
VALUES('def'),('ghi'); --Will get 2 and 3.
SELECT *
FROM dbo.YourTable;
DELETE FROM dbo.YourTable;
INSERT INTO dbo.YourTable (SomeCol)
VALUES('abc'); --Will get ID 4, because 1-3 have been used. Deleting doesn't let you reuse values.
SELECT *
FROM dbo.YourTable;
DELETE FROM dbo.YourTable;
DBCC CHECKIDENT ('dbo.YourTable', RESEED, 1);
INSERT INTO dbo.YourTable (SomeCol)
VALUES('abc'); --Will get ID 2, as you seeded back to 1; so the NEXT ID is used.
SELECT *
FROM dbo.YourTable;
TRUNCATE TABLE dbo.YourTable;
INSERT INTO dbo.YourTable (SomeCol)
VALUES('abc'); --Will get ID 4, because 1-3 have been used.
SELECT *
FROM dbo.YourTable; --Will get ID 1, as the column was reseed with the TRUNCATE
DROP TABLE dbo.YourTable;
For your specific question on reseeding, the next value after the seed your define is use. The seed you define is the one you are saying was last used. This is covered in the documentation Forcing the current identity value to a new value:
Because the table has existing rows, the next row inserted will use 11
as the value – the new current identity value defined for the column
plus 1 (which is the column's increment value).
The only way to define a table doesn't have existing rows is the TRUNCATE it, which is what I do later on in the above batch (and why 1 is reused).
At the end of the day, the value of your IDENTITY is meaningless other than to provide the row with a single use value (which is not guarenteed to be unique on it's own). Combined with the Primary key/Unique constraints, it makes a good Clustered index candidate, as the next value is always greater than the last used, and values aren't reused.
If having sequential values is important, then what you need to use is a SEQUENCE, not the IDENTITY property. The latter doesn't guarantee uniqueness, or sequential values on it's own (as they could be skipped due to deletes, failed inserts, an unexpected shutdown, etc), but it does guarantee it will not reuse values once they have been (without a RESEED): IDENTITY (Transact-SQL) - Remarks. A SEQUENCE can be used to ensure the values are indeed sequential (apart from due to a DELETE).
Welcome to the forum :)
If you created the table using
Id INT IDENTITY(1,1)
Then the first record inserted will have Id = 1, however, if the insert statement fails or the transaction is rolled back the consumed identity be marked as used (or lost) and the next insert statement will proceed from Id = 2.
Have a look at Microsoft documentation on this topic:
https://learn.microsoft.com/en-us/sql/t-sql/statements/create-table-transact-sql-identity-property?view=sql-server-2017
When deleting inserted rows (which also happens when those inserts are rolled-back in a transaction, by the way), the identity value is not automatically reset. The identity functionality "remembers" its last value.
Gaps in the identity values will also NOT be filled when older records are deleted from the table and new records are inserted into the table.
That's just how identity works. It's a simple and safe mechanism.
If you (occasionally!) want to reset the identity value, you can take a look at DBCC CHECKIDENT. I personally tend to use it like this:
DBCC CHECKIDENT (MyTable, RESEED, 0) WITH NO_INFOMSGS;
DBCC CHECKIDENT (MyTable, RESEED) WITH NO_INFOMSGS;
(I execute both lines, in this order.)
I would advice against this practice in production environments, however.
i got a function in sql that generate sequential series of alphanumeric
no.like (c000,c0001 .......) , which is working good . but when i deleted all data in table , it starts from last generated no. i want it to reset its value from "c0000" .
code is as follows :-
create table Customers
(
dbID int identity not null primary key,
CustomerName varchar(100)
)
create function CustomerNumber (#id int)
returns char(5)
as
begin
return 'C' + right('0000' + convert(varchar(10), #id), 4)
end
alter table Customers add CustomerNumber as dbo.CustomerNumber(dbID)
thanks in advance....
EDIT 1 -
how to update it to increment based on last value . means if last entry having no. c0053 , and i deleted this record , so when next entry added it should have value "C0053" not "C0054".
thanks
Truncate Table Command is good way to reset Identity, but there is other command also to reset Identity after deletion of records.
DBCC CHECKIDENT (TableName, RESEED, 0)
After Deleting you can use this command to reset Identity to 0.
TRUNCATE TABLE
Removes all rows from a table or specified partitions of a table, without logging the individual row deletions. TRUNCATE TABLE is similar to the DELETE statement with no WHERE clause; however, TRUNCATE TABLE is faster and uses fewer system and transaction log resources.
TRUNCATE TABLE Customers
or remove your in build function.
My suggestion is instead of deleting all rows of data why dont you truncate the table.
If you are truncate the table it automatically reset your auto increment to 0
TRUNCATE TABLE your_table_name;
This example would truncate the table and remove all records from that table. and rest your auto increment too.
The SQL TRUNCATE TABLE command is used to delete complete data from an existing table
Try this way. May help you.
I ran a delete script to delete all rows that had an id greater than 0 to clear the table and now when I try to add rows to the table, the id starts off where it left off from before. How can I delete the info in the table so the id starts off at 1 again?
Delete statement doesnt reset the identity value. Use Truncate table command if you want identity value to be reset. something like this..
TRUNCATE TABLE Table_Name
This will empty the table and reset the identity value.
Only use TRUNCATE when you want all the rows to be deleted. As it does not allow you to use WHERE clause.
I don't think that is possible in the same table. Which database are you using? In previous versions of MS Access compacting the database used to work but not any more. I don't think SQL Server allows that either. The only way is to copy the records from this table to a new table, delete the old table and rename the new table to the old table name.
In MS-SQL you can have a play with DBCC CHECKIDENT (yourtable, reseed, 0)
in SQL SERVER 2010, I deleted some columns that made use of identity fields.
I like to insert rows where the identity columns were deleted with the original values but not sure how to do so.
I tried edit but the identity columns were greyed out
UPDATE table
SET IDENTITY_INSERT [YourTableName] ON
--do your update/insert query here
SET IDENTITY_INSERT [YourTableName] OFF
Can you explain why you care whether there are gaps in your identity columns? If you just want some pretty ID number next to a label (and aren't worried about related data in other tables, or whether the 2nd row retains the ID 2 even if ID 1 is deleted), you can always derive these meaningless ID numbers at runtime, e.g.
SELECT col, MeaninglessID = ROW_NUMBER() OVER (ORDER BY col)
FROM dbo.table
ORDER BY col;
You need to reseed the identity:
dbcc checkident (mytable, reseed, 30)
Is it possible to reseed an auto increment column in a SQLite database, and if so, how is this done?
ie. The equivalent of DBCC CHECKIDENT ('MyTable', RESEED, 1) in SQL Server.
In SQLite there is a table named SQLITE_SEQUENCE, which tracks the largest RowId value that a table has. You can do insert, updates and deletes on this table. For example, to mimic similar functionality as the TRUNCATE TABLE statement SQL Server you could something like:
DELETE FROM MyTableName;
DELETE FROM SQLITE_SEQUENCE WHERE NAME = 'MyTableName';
In the above example all data from MyTableName is removed, and the auto increment rowid is reset by removing the value from the SQLITE_SEQUENCE table. See the documentation for AUTOINCREMENT for more information.
DELETE
FROM MyTableName
select *
from SQLITE_SEQUENCE
update SQLITE_SEQUENCE
set seq = 0
where name ='MyTableName'
Alternatively you could export a SQL file from the SQLite database. Then edit the generated SQL file and update the appropriate entries to the desired IDs or delete the INSERT statements. After this create a new empty database and seed it with the adjusted SQL file. The highest ID + 1 will then be the ID for a new entry...
With this way you can decide, which entries to keep and which entries should be removed as a non-destructive or even a more flexible approach.
For me it worked - clean and easy. ;)