[sql] Best way to get identity of inserted row?

What is the best way to get IDENTITY of inserted row?

I know about @@IDENTITY and IDENT_CURRENT and SCOPE_IDENTITY but don't understand the pros and cons attached to each.

Can someone please explain the differences and when I should be using each?

After Your Insert Statement you need to add this. And Make sure about the table name where data is inserting.You will get current row no where row affected just now by your insert statement.

IDENT_CURRENT('tableName')

I believe the safest and most accurate method of retrieving the inserted id would be using the output clause.

for example (taken from the following MSDN article)

USE AdventureWorks2008R2;
GO
DECLARE @MyTableVar table( NewScrapReasonID smallint,
                           Name varchar(50),
                           ModifiedDate datetime);
INSERT Production.ScrapReason
    OUTPUT INSERTED.ScrapReasonID, INSERTED.Name, INSERTED.ModifiedDate
        INTO @MyTableVar
VALUES (N'Operator error', GETDATE());

--Display the result set of the table variable.
SELECT NewScrapReasonID, Name, ModifiedDate FROM @MyTableVar;
--Display the result set of the table.
SELECT ScrapReasonID, Name, ModifiedDate 
FROM Production.ScrapReason;
GO

From MSDN

@@IDENTITY, SCOPE_IDENTITY, and IDENT_CURRENT are similar functions in that they return the last value inserted into the IDENTITY column of a table.

@@IDENTITY and SCOPE_IDENTITY will return the last identity value generated in any table in the current session. However, SCOPE_IDENTITY returns the value only within the current scope; @@IDENTITY is not limited to a specific scope.

IDENT_CURRENT is not limited by scope and session; it is limited to a specified table. IDENT_CURRENT returns the identity value generated for a specific table in any session and any scope. For more information, see IDENT_CURRENT.

• IDENT_CURRENT is a function which takes a table as a argument.
• @@IDENTITY may return confusing result when you have an trigger on the table
• SCOPE_IDENTITY is your hero most of the time.

Even though this is an older thread, there is a newer way to do this which avoids some of the pitfalls of the IDENTITY column in older versions of SQL Server, like gaps in the identity values after server reboots. Sequences are available in SQL Server 2016 and forward which is the newer way is to create a SEQUENCE object using TSQL. This allows you create your own numeric sequence object in SQL Server and control how it increments.

Here is an example:

CREATE SEQUENCE CountBy1  
    START WITH 1  
    INCREMENT BY 1 ;  
GO  

Then in TSQL you would do the following to get the next sequence ID:

SELECT NEXT VALUE FOR CountBy1 AS SequenceID
GO

Here are the links to CREATE SEQUENCE and NEXT VALUE FOR

Create a uuid and also insert it to a column. Then you can easily identify your row with the uuid. Thats the only 100% working solution you can implement. All the other solutions are too complicated or are not working in same edge cases. E.g.:

1) Create row

INSERT INTO table (uuid, name, street, zip) 
        VALUES ('2f802845-447b-4caa-8783-2086a0a8d437', 'Peter', 'Mainstreet 7', '88888');

2) Get created row

SELECT * FROM table WHERE uuid='2f802845-447b-4caa-8783-2086a0a8d437';

When you use Entity Framework, it internally uses the OUTPUT technique to return the newly inserted ID value

DECLARE @generated_keys table([Id] uniqueidentifier)

INSERT INTO TurboEncabulators(StatorSlots)
OUTPUT inserted.TurboEncabulatorID INTO @generated_keys
VALUES('Malleable logarithmic casing');

SELECT t.[TurboEncabulatorID ]
FROM @generated_keys AS g 
   JOIN dbo.TurboEncabulators AS t 
   ON g.Id = t.TurboEncabulatorID 
WHERE @@ROWCOUNT > 0

The output results are stored in a temporary table variable, joined back to the table, and return the row value out of the table.

Note: 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.

This technique (OUTPUT) is only available on SQL Server 2008 or newer.

Edit - The reason for the join

The reason that Entity Framework joins back to the original table, rather than simply use the OUTPUT values is because EF also uses this technique to get the rowversion of a newly inserted row.

You can use optimistic concurrency in your entity framework models by using the Timestamp attribute:

public class TurboEncabulator
{
   public String StatorSlots)

   [Timestamp]
   public byte[] RowVersion { get; set; }
}

When you do this, Entity Framework will need the rowversion of the newly inserted row:

DECLARE @generated_keys table([Id] uniqueidentifier)

INSERT INTO TurboEncabulators(StatorSlots)
OUTPUT inserted.TurboEncabulatorID INTO @generated_keys
VALUES('Malleable logarithmic casing');

SELECT t.[TurboEncabulatorID], t.[RowVersion]
FROM @generated_keys AS g 
   JOIN dbo.TurboEncabulators AS t 
   ON g.Id = t.TurboEncabulatorID 
WHERE @@ROWCOUNT > 0

And in order to retrieve this Timetsamp you cannot use an OUTPUT clause.

That's because if there's a trigger on the table, any Timestamp you OUTPUT will be wrong:

• Initial insert. Timestamp: 1
• OUTPUT clause outputs timestamp: 1
• trigger modifies row. Timestamp: 2

The returned timestamp will never be correct if you have a trigger on the table. So you must use a separate SELECT.

And even if you were willing to suffer the incorrect rowversion, the other reason to perform a separate SELECT is that you cannot OUTPUT a rowversion into a table variable:

DECLARE @generated_keys table([Id] uniqueidentifier, [Rowversion] timestamp)

INSERT INTO TurboEncabulators(StatorSlots)
OUTPUT inserted.TurboEncabulatorID, inserted.Rowversion INTO @generated_keys
VALUES('Malleable logarithmic casing');

The third reason to do it is for symmetry. When performing an UPDATE on a table with a trigger, you cannot use an OUTPUT clause. Trying do UPDATE with an OUTPUT is not supported, and will give an error:

• Cannot use UPDATE with OUTPUT clause when a trigger is on the table

The only way to do it is with a follow-up SELECT statement:

UPDATE TurboEncabulators
SET StatorSlots = 'Lotus-O deltoid type'
WHERE ((TurboEncabulatorID = 1) AND (RowVersion = 792))

SELECT RowVersion
FROM TurboEncabulators
WHERE @@ROWCOUNT > 0 AND TurboEncabulatorID = 1

I can't speak to other versions of SQL Server, but in 2012, outputting directly works just fine. You don't need to bother with a temporary table.

INSERT INTO MyTable
OUTPUT INSERTED.ID
VALUES (...)

By the way, this technique also works when inserting multiple rows.

INSERT INTO MyTable
OUTPUT INSERTED.ID
VALUES
    (...),
    (...),
    (...)

Output

ID
2
3
4

I'm saying the same thing as the other guys, so everyone's correct, I'm just trying to make it more clear.

@@IDENTITY returns the id of the last thing that was inserted by your client's connection to the database.
Most of the time this works fine, but sometimes a trigger will go and insert a new row that you don't know about, and you'll get the ID from this new row, instead of the one you want

SCOPE_IDENTITY() solves this problem. It returns the id of the last thing that you inserted in the SQL code you sent to the database. If triggers go and create extra rows, they won't cause the wrong value to get returned. Hooray

IDENT_CURRENT returns the last ID that was inserted by anyone. If some other app happens to insert another row at an unforunate time, you'll get the ID of that row instead of your one.

If you want to play it safe, always use SCOPE_IDENTITY(). If you stick with @@IDENTITY and someone decides to add a trigger later on, all your code will break.

Add

SELECT CAST(scope_identity() AS int);

to the end of your insert sql statement, then

NewId = command.ExecuteScalar()

will retrieve it.

The best (read: safest) way to get the identity of a newly-inserted row is by using the output clause:

create table TableWithIdentity
           ( IdentityColumnName int identity(1, 1) not null primary key,
             ... )

-- type of this table's column must match the type of the
-- identity column of the table you'll be inserting into
declare @IdentityOutput table ( ID int )

insert TableWithIdentity
     ( ... )
output inserted.IdentityColumnName into @IdentityOutput
values
     ( ... )

select @IdentityValue = (select ID from @IdentityOutput)

@@IDENTITY is the last identity inserted using the current SQL Connection. This is a good value to return from an insert stored procedure, where you just need the identity inserted for your new record, and don't care if more rows were added afterward.

SCOPE_IDENTITY is the last identity inserted using the current SQL Connection, and in the current scope -- that is, if there was a second IDENTITY inserted based on a trigger after your insert, it would not be reflected in SCOPE_IDENTITY, only the insert you performed. Frankly, I have never had a reason to use this.

IDENT_CURRENT(tablename) is the last identity inserted regardless of connection or scope. You could use this if you want to get the current IDENTITY value for a table that you have not inserted a record into.

ALWAYS use scope_identity(), there's NEVER a need for anything else.

One other way to guarantee the identity of the rows you insert is to specify the identity values and use the SET IDENTITY_INSERT ON and then OFF. This guarantees you know exactly what the identity values are! As long as the values are not in use then you can insert these values into the identity column.

CREATE TABLE #foo 
  ( 
     fooid   INT IDENTITY NOT NULL, 
     fooname VARCHAR(20) 
  ) 

SELECT @@Identity            AS [@@Identity], 
       Scope_identity()      AS [SCOPE_IDENTITY()], 
       Ident_current('#Foo') AS [IDENT_CURRENT] 

SET IDENTITY_INSERT #foo ON 

INSERT INTO #foo 
            (fooid, 
             fooname) 
VALUES      (1, 
             'one'), 
            (2, 
             'Two') 

SET IDENTITY_INSERT #foo OFF 

SELECT @@Identity            AS [@@Identity], 
       Scope_identity()      AS [SCOPE_IDENTITY()], 
       Ident_current('#Foo') AS [IDENT_CURRENT] 

INSERT INTO #foo 
            (fooname) 
VALUES      ('Three') 

SELECT @@Identity            AS [@@Identity], 
       Scope_identity()      AS [SCOPE_IDENTITY()], 
       Ident_current('#Foo') AS [IDENT_CURRENT] 

-- YOU CAN INSERT  
SET IDENTITY_INSERT #foo ON 

INSERT INTO #foo 
            (fooid, 
             fooname) 
VALUES      (10, 
             'Ten'), 
            (11, 
             'Eleven') 

SET IDENTITY_INSERT #foo OFF 

SELECT @@Identity            AS [@@Identity], 
       Scope_identity()      AS [SCOPE_IDENTITY()], 
       Ident_current('#Foo') AS [IDENT_CURRENT] 

SELECT * 
FROM   #foo 

This can be a very useful technique if you are loading data from another source or merging data from two databases etc.