I have a table in a SQL Server database that has an auto-generated integer primary key. Without inserting a record into the table, I need to query the database and get what the next auto-generated ID number will be.
I think it's SQL Server version 2005, if that makes a difference.
Is there a way to do this?
Yes, but it's unreliable because another session might use the expected number.
If you still want to do this, use IDENT_CURRENT
Edit, as the comments have pointed out (improving my answer):
you need to add one IDENT_INCR('MyTable') to this to get the potential next number
another process may rollback and this number may not be the one used anyway
No, there is not. The ID will only ever be defined and handed out when the actual INSERT happens.
You can check the last given ID by using
DBCC CHECKIDENT('YourTableName')
but that's just the last one used - no guarantee that the next one is really going to be this value + 1 - it could be - but no guarantees
The only way to get a number that is guranteed not to be used by another process (i.e., a race condition) is to do the insert - is there any reason you can't do a NULL insert (i.e., just insert into the table with NULLs or default values for all other columns) and then subsequently UPDATE it?
i.e.,
CREATE TABLE bob (
seq INTEGER IDENTITY (1,1) NOT NULL,
col1 INTEGER NULL
)
GO
DECLARE #seqid INTEGER
INSERT INTO bob DEFAULT VALUES
SET #seqid = SCOPE_IDENTITY()
-- do stuff with #seqid
UPDATE bob SET col1 = 42 WHERE seq = #seqid
GO
You shouldn't use the technique in code, but if you need to do it for investigative purposes:
select ident_current(‘foo’) + ident_incr(‘foo’)
That gives you the last value generated + the incrementation for the identity, so should represent the next choice SQL would make without inserting a row to find out. This is a correct value even if a rollback has pushed the value forwards - but again, this is investigative SQL not stuff I would put in code.
The two values can also be found in the sys.identity_values DMV, the fields are increment_value and last_value.
Another way, depending on what your doing, is inserting whatever data goes into the table, and then using ##identity to retrieve the id of the record inserted.
example:
declare #table table (id int identity(1,1), name nvarchar(10))
insert into #table values ('a')
insert into #table values ('b')
insert into #table values ('c')
insert into #table values ('d')
select ##identity
insert into #table values ('e')
insert into #table values ('f')
select ##identity
This is pretty much a bad idea straight off the bat, but if you don't anticipate high volume and/or concurrency issues, you could just do something like this
select #nextnum = max(Id) + 1 from MyTable
I don't think thats possible out of the box in MS SQL (any version). You can do this with column type uniqueidentifier and using function NEWID().
For int column, you would have to implement your own sequential generator.
Related
I have an existing table that has an identity column and a column that has a constraint to ensure that it matches the value in the identity column.
(I know that this is not a good design, but it is an old table that can not be changed at the moment)
I know that I can use the IDENT_CURRENT('mytable') as a value during the insert to put the newly created identity value into the other column (FakeID).
INSERT INTO MyTable (FakeID)
SELECT IDENT_CURRENT('MyTable')
I have seen that this has issues when inserting multiple records, but for this use I am only inserting a single record.
My question is how safe is this to use?
Mainly, is there a risk from inserts made under different sessions or in a different scope?
Also, does this behave as expected when the table is truncated?
Any other suggestions are welcome.
SCOPE_IDENTITY() is going to be a safer bet here. If someone inserts into the table before this part of your transaction runs, IDENT_CURRENT will grab the newly generated Id from the other transaction.
So I would declare a variable and set its value to SCOPE_IDENTITY(), something like this
DECLARE #Id INT
SET #Id = SCOPE_IDENTITY()
INSERT INTO MyTable (FakeID)
SELECT #Id
Here are some posts on a similar issue:
http://bytes.com/topic/sql-server/answers/471026-ident_current-problem
IDENT_CURRENT equivalent for current session
I'm trying to get a the key-value back after an INSERT-statement.
Example:
I've got a table with the attributes name and id. id is a generated value.
INSERT INTO table (name) VALUES('bob');
Now I want to get the id back in the same step. How is this done?
We're using Microsoft SQL Server 2008.
No need for a separate SELECT...
INSERT INTO table (name)
OUTPUT Inserted.ID
VALUES('bob');
This works for non-IDENTITY columns (such as GUIDs) too
Use SCOPE_IDENTITY() to get the new ID value
INSERT INTO table (name) VALUES('bob');
SELECT SCOPE_IDENTITY()
http://msdn.microsoft.com/en-us/library/ms190315.aspx
INSERT INTO files (title) VALUES ('whatever');
SELECT * FROM files WHERE id = SCOPE_IDENTITY();
Is the safest bet since there is a known issue with OUTPUT Clause conflict on tables with triggers. Makes this quite unreliable as even if your table doesn't currently have any triggers - someone adding one down the line will break your application. Time Bomb sort of behaviour.
See msdn article for deeper explanation:
http://blogs.msdn.com/b/sqlprogrammability/archive/2008/07/11/update-with-output-clause-triggers-and-sqlmoreresults.aspx
Entity Framework performs something similar to gbn's answer:
DECLARE #generated_keys table([Id] uniqueidentifier)
INSERT INTO Customers(FirstName)
OUTPUT inserted.CustomerID INTO #generated_keys
VALUES('bob');
SELECT t.[CustomerID]
FROM #generated_keys AS g
JOIN dbo.Customers AS t
ON g.Id = t.CustomerID
WHERE ##ROWCOUNT > 0
The output results are stored in a temporary table variable, and then selected back to the client. Have to be aware of the gotcha:
inserts can generate more than one row, so the variable can hold more than one row, so you can be returned more than one ID
I have no idea why EF would inner join the ephemeral table back to the real table (under what circumstances would the two not match).
But that's what EF does.
SQL Server 2008 or newer only. If it's 2005 then you're out of luck.
There are many ways to exit after insert
When you insert data into a table, you can use the OUTPUT clause to
return a copy of the data that’s been inserted into the table. The
OUTPUT clause takes two basic forms: OUTPUT and OUTPUT INTO. Use the
OUTPUT form if you want to return the data to the calling application.
Use the OUTPUT INTO form if you want to return the data to a table or
a table variable.
DECLARE #MyTableVar TABLE (id INT,NAME NVARCHAR(50));
INSERT INTO tableName
(
NAME,....
)OUTPUT INSERTED.id,INSERTED.Name INTO #MyTableVar
VALUES
(
'test',...
)
IDENT_CURRENT: It returns the last identity created for a particular table or view in any session.
SELECT IDENT_CURRENT('tableName') AS [IDENT_CURRENT]
SCOPE_IDENTITY: It returns the last identity from a same session and the same scope. A scope is a stored procedure/trigger etc.
SELECT SCOPE_IDENTITY() AS [SCOPE_IDENTITY];
##IDENTITY: It returns the last identity from the same session.
SELECT ##IDENTITY AS [##IDENTITY];
##IDENTITY Is a system function that returns the last-inserted identity value.
There are multiple ways to get the last inserted ID after insert command.
##IDENTITY : It returns the last Identity value generated on a Connection in current session, regardless of Table and the scope of statement that produced the value
SCOPE_IDENTITY(): It returns the last identity value generated by the insert statement in the current scope in the current connection regardless of the table.
IDENT_CURRENT(‘TABLENAME’) : It returns the last identity value generated on the specified table regardless of Any connection, session or scope. IDENT_CURRENT is not limited by scope and session; it is limited to a specified table.
Now it seems more difficult to decide which one will be exact match for my requirement.
I mostly prefer SCOPE_IDENTITY().
If you use select SCOPE_IDENTITY() along with TableName in insert statement, you will get the exact result as per your expectation.
Source : CodoBee
The best and most sure solution is using SCOPE_IDENTITY().
Just you have to get the scope identity after every insert and save it in a variable because you can call two insert in the same scope.
ident_current and ##identity may be they work but they are not safe scope. You can have issues in a big application
declare #duplicataId int
select #duplicataId = (SELECT SCOPE_IDENTITY())
More detail is here Microsoft docs
You can use scope_identity() to select the ID of the row you just inserted into a variable then just select whatever columns you want from that table where the id = the identity you got from scope_identity()
See here for the MSDN info http://msdn.microsoft.com/en-us/library/ms190315.aspx
Recommend to use SCOPE_IDENTITY() to get the new ID value, But NOT use "OUTPUT Inserted.ID"
If the insert statement throw exception, I except it throw it directly. But "OUTPUT Inserted.ID" will return 0, which maybe not as expected.
This is how I use OUTPUT INSERTED, when inserting to a table that uses ID as identity column in SQL Server:
'myConn is the ADO connection, RS a recordset and ID an integer
Set RS=myConn.Execute("INSERT INTO M2_VOTELIST(PRODUCER_ID,TITLE,TIMEU) OUTPUT INSERTED.ID VALUES ('Gator','Test',GETDATE())")
ID=RS(0)
You can append a select statement to your insert statement.
Integer myInt =
Insert into table1 (FName) values('Fred'); Select Scope_Identity();
This will return a value of the identity when executed scaler.
* Parameter order in the connection string is sometimes important. * The Provider parameter's location can break the recordset cursor after adding a row. We saw this behavior with the SQLOLEDB provider.
After a row is added, the row fields are not available, UNLESS the Provider is specified as the first parameter in the connection string. When the provider is anywhere in the connection string except as the first parameter, the newly inserted row fields are not available. When we moved the the Provider to the first parameter, the row fields magically appeared.
After doing an insert into a table with an identity column, you can reference ##IDENTITY to get the value:
http://msdn.microsoft.com/en-us/library/aa933167%28v=sql.80%29.aspx
In SQL Server 2005 I am inserting a row into a table using a stored procedure and I want to fetch the new primary key value just after inserting that row. I am using following approach to get primary key value after insertion row
Create Proc Sp_Test
#testEmail varchar(20)=null,-- Should be Unique
#testName varchar(20)=null -- Should be Unique
as
begin
insert into tableTest (testUserEmail,testUserName)values (#testValue,#testName)
select MAX(ID) from tableTest --ID is Primary Key
--or
select ID from tableTest where testUserEmail =#testValue and testUserName = #testName
--or
select SCOPE_IDENTITY() as ID
end
Please suggest me which approach is better to perform described task.
By all means - use the SCOPE_IDENTITY() if your ID column is an INT IDENTITY - only that will give you the correct results!
The first approach with the MAX(ID) will fail terribly if you have multiple clients inserting rows almost at the same time - you'll get false results back. Don't use that!
The third approach might fail if another entry with the same values for E-Mail and name already exists.
Also, as a side-note: you should never use sp_ as your prefix! This is a Microsoft-reserved prefix and has downsides in terms of performance - use something else.
If you have an Identity column as primary key you should use SCOPE_IDENTITY()
You could also use the OUTPUT Clause to return the ID.
insert into tableTest(testUserEmail,testUserName)
output inserted.ID
values (#testValue, #testName)
I defined a database using SQL Server 2008 R2 Express, and connected to it using Visual Basic 2010 Express. For some reason though, when I use the database in the program, it wants to start off using a negative primary key.
Is there any way to make the primary key only a positive number?
In addition to #RNarry Young response. You can check the schema if your table
Suppose you have the following table
create table #t
(
ID int Identity(-1, 1),
s varchar(100)
)
Now you make two inserts
Insert into #t(s) values('ed')
Insert into #t(s) values('ed')
Check the output
select * from #t
It shows like below. If you see the screen shot. The first row shows -1 in the primary key value. Due to the reason that the Identity Seed is -1 mentioned in the schema.
You can get rid of this issue. We should use the schema like below.
create table #t
(
ID int Identity(1, 1),
s varchar(100)
)
Following is the other way to generate
Set Identity_Insert #t On
Insert into #t(ID, s) values(-1, 'ed')
Set Identity_Insert #t OFF
Set Identity_Insert #t On
Insert into #t(ID, s) values(-2, 'ed')
Set Identity_Insert #t OFF
Off hand I can only think of two things that would cause this:
When creating the table you (or some software/code you are using) is setting the Identity seed to a negative number.
Or, you (or some software/code you are using) are using Identity_Insert and just forcing a negative number in.
The identity seed for the table will be visible within SSMS.
But.... it doesn't matter in the slightest that it's producing negative numbers. There's only really two practical concerns about your identiity value:
Unique values
Sufficient space to cover the expected range of values (so, a tinyint key wouldn't be great for tracking the entire world population...)
Once they're sorted, the actual values shouldn't be of any concern at all. They're internal to the database.
Hi I want to have two tables each have an INT "id" column which will auto-increment but I don't want either "id" columns to ever share the same number. What is this called and what's the best way to do it? Sequence? Iterator? Index? Incrementor?
Motivation: we're migrating from one schema to a another and have a web-page that reads both tables and shows the (int) ID, but I can't have the same ID used for both tables.
I'm using SQL Server 9.0.3068.
Thanks!
Just configure the identity increment to be >1 e.g. table one uses IDENTITY (1, 10) [1,11,21...] and table two uses IDENTITY (2, 10) [2,12,22...]. This will also give you some room for expansion if needed later.
I think using a GUID would be the most straightforward way, if I understand you correctly.
SELECT NEWID()
Use a column with GUID (Globally Unique Identifier) type. It's 16 byte and will be always unique for each row.
Just be aware that you'll get a significant performance hit comparing to normal integer keys.
Use another table with an ID key of type int default it to 1, called KeyID or whatever.
Have a stored procedure retrieve the value, add 1, then update the KeyID, then return this to the stored procedure which is updating your two tables which needs the new unique key.
This will ensure the ID is an int, and that it's unique between the set of tables which are using the stored procedure to generate new ID's.
You can define an IDENTITY column in a third table, use that to generate ID values, but you always roll back any inserts you make into the table (to avoid making it grow). Rolling back the transaction doesn't roll back the fact that the ID was generated.
I'm not a regular user of Microsoft SQL Server, so please forgive any syntax gaffes. But something like the following is what I have in mind:
CREATE TABLE AlwaysRollback (
id IDENTITY(1,1)
);
BEGIN TRANSACTION;
INSERT INTO AllwaysRollBack () VALUES ();
ROLLBACK TRANSACTION;
INSERT INTO RealTable1 (id, ...) VALUES (SCOPE_IDENTITY(), ...);
BEGIN TRANSACTION;
INSERT INTO AllwaysRollBack () VALUES ();
ROLLBACK TRANSACTION;
INSERT INTO RealTable2 (id, ...) VALUES (SCOPE_IDENTITY(), ...);
I don't know what you would call it.
If you don't want to use a GUID or a separate table, you could also create a function that looked at the max values of the ids from both tables and added one to the that value (or something like that).
You could then call that function in an insert trigger on both tables.
I am personally a fan of the GUID solution, but here is a viable option.
Many solutions to this problem have avoided GUID and used good old integer. This is common also with merge replication situations where many satellite sites merge with a master and key conflicts need to be avoided.
If GUID will not work for you, and you absolutely must have int, bigint, or the like, you can always just use an IDENTITY column and have each table with a different value for SEED. Those datatypes have a very wide range, and it is not too hard to split the range into usable segments, especially if all you want is two splits. As an example, basic int has a range from -2^31 (-2,147,483,648) through 2^31 - 1 (2,147,483,647). This is more than enough for a customer table, for example.
Transact-SQL Reference (SQL Server 2000)
int, bigint, smallint, and tinyint
Example:
--Create table with a seed of 1 billion and an increment of 1
CREATE TABLE myTable
(
primaryKey int IDENTITY (1000000000, 1),
columnOne varchar(10) NOT NULL
)
If you really need to do this with an int and you have an auto incrementing number, the way i have done this before is to change the id field auto increment function to the sequence of the other table. I am not too sure in ms sql or my sql but in pgsql that means that in the sql you would have this field
id integer NOT NULL DEFAULT nextval('table_two_seq'::regclass),
where table_two_sequence is the sequence function for the other table. Then test it out by inserting some data. I am really sorry if this wont work in ms sql i try to steer clear of it tbh. Failing that the GUID is the best way as has been mentioned by others. Or when inserting in the code that you use you could put an algorithm in that but it could get messy.
Alternatively, think about having the data in one table as this would be a way around it. if you need to you could have a view simulating two tables. Just a thought.
Hope i have helped
Starting with SQL Server 2012 you can declare a sequence object
https://msdn.microsoft.com/en-us/library/ff878091.aspx which is exactly what you need.
I should be pretty trivial to emulate a sequence object with a table
containing the next sequence value and a stored procedure atomically
select the value and increment. [You'd liked to use function, but functions
can't have side effects.]
How about this hack? Create a table (MySequence) with two columns: And Identity column (SequenceValue) and a dummy column (DummyValue) and use this stored procedure to get a new sequence value. The only row in the table will be last sequence value retrieved.
CREATE PROCEDURE GetNextValue
AS
BEGIN
DECLARE #value int = null;
-- Insert statements for procedure here
INSERT into MySequence (DummyValue) Values (null);
SET #value = SCOPE_IDENTITY();
DELETE from MySequence where SequenceValue <> #value
SELECT #value as Sequence
return #value
END
To use the sequence you'd have to manage the inserts to the target tables--a trigger would probably work.