How am I supposed to get the IDENTITY of an inserted row?
I know about ##IDENTITY and IDENT_CURRENT and SCOPE_IDENTITY, but don't understand the implications or impacts attached to each.
Can someone please explain the differences and when I would be using each?
##IDENTITY returns the last identity value generated for any table in the current session, across all scopes. You need to be careful here, since it's across scopes. You could get a value from a trigger, instead of your current statement.
SCOPE_IDENTITY() returns the last identity value generated for any table in the current session and the current scope. Generally what you want to use.
IDENT_CURRENT('tableName') returns the last identity value generated for a specific table in any session and any scope. This lets you specify which table you want the value from, in case the two above aren't quite what you need (very rare). Also, as #Guy Starbuck mentioned, "You could use this if you want to get the current IDENTITY value for a table that you have not inserted a record into."
The OUTPUT clause of the INSERT statement will let you access every row that was inserted via that statement. Since it's scoped to the specific statement, it's more straightforward than the other functions above. However, it's a little more verbose (you'll need to insert into a table variable/temp table and then query that) and it gives results even in an error scenario where the statement is rolled back. That said, if your query uses a parallel execution plan, this is the only guaranteed method for getting the identity (short of turning off parallelism). However, it is executed before triggers and cannot be used to return trigger-generated values.
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
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.
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)
Add
SELECT CAST(scope_identity() AS int);
to the end of your insert sql statement, then
NewId = command.ExecuteScalar()
will retrieve it.
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.
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
##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.
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';
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
Complete solution in SQL and ADO.NET
const string sql = "INSERT INTO [Table1] (...) OUTPUT INSERTED.Id VALUES (...)";
using var command = connection.CreateCommand();
command.CommandText = sql;
var outputIdParameter = new SqlParameter("#Id", SqlDbType.Int) { Direction = ParameterDirection.Output };
command.Parameters.Add(outputIdParameter);
await connection.OpenAsync();
var outputId= await command.ExecuteScalarAsync();
await connection.CloseAsync();
int id = Convert.ToInt32(outputId);
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 am attempting to get the OUTPUT table from an INSERT command on a SQL Server database (v14).
DECLARE #i TABLE (TICKET_ID int, CREATED_DATE datetime);
INSERT INTO dbo.TICKET (SITE_ID, TICKET_TITLE, USER_ID)
OUTPUT INSERTED.TICKET_ID, INSERTED.CREATED_DATE INTO #i
VALUES (#s, #t, #q);
SELECT * FROM #i;
I have 3 parameters that are being populated for the site, ticket title and user by #s, #t and #u respectively.
I am calling the command using a SqlClient.SqlDataReader Object with ExecuteReader Function on the 4.5 Framework.
The command successfully inserts the record into the database table, but does not return the table #i with the ticket ID (Auto Increment) and created date (default =GETDATE) which is what I am expected to present to the user once saved to the database.
I have played around with the removing of the #i TABLE in the command, but I get a .NET error:
The target table 'name' of the DML statement cannot have any enabled triggers if the statement contains an OUTPUT clause without INTO clause
I have found a couple of links that provide some ways to fix these but it did not fix my issue
https://learn.microsoft.com/en-us/previous-versions/dotnet/articles/ms971497(v=msdn.10)?redirectedfrom=MSDN
Cannot use UPDATE with OUTPUT clause when a trigger is on the table
Is there any assistance that can be provided to assist in what I am trying to achieve?
It seems a pain to have to but another option might be just to do this:
INSERT INTO dbo.TICKET (SITE_ID, TICKET_TITLE, USER_ID)
VALUES (#s, #t, #q);
SELECT TICKET_ID, CREATED_DATE
FROM dbo.TICKET
WHERE SITE_ID = #s AND TICKET_TITLE = #t AND USER_ID = #q;
I don't know why you'd need the table. I think you need to just execute this:
INSERT INTO dbo.TICKET (SITE_ID, TICKET_TITLE, USER_ID)
OUTPUT inserted.TICKET_ID, inserted.CREATED_DATE
VALUES (#s, #t, #q);
I can't see any value in the table. When you execute this statement, it'll return results to the client, just like a SELECT statement would.
Hope that helps.
I have a table in SQL Server called Test_Table with two columns: ID and Name
The table looks something like this:
ID NAME
--------
1 John
2 Jane
Now I have a stored procedure which inserts records into this.
INSERT INTO Test_Table
VALUES (#Id,#Name)
And I'm passing this values from my c# code. Now I want to modify this so that the table does not have duplicates. Where should I check this, In the code or the DB? I'm very weak in DB side stuff. So how can I handle duplicates before inserting values in my table
The "right" way to do that is in DB because:
Don't need to read all DB
Need to pass all data to C# which increase the IO
Concurrency - if you have more than 1 C# application you will need to sync them vs in DB it would be simpler
You can define the column as unique or key, which will prevent duplicate values ,DB will take care of it
If you use MSSQL use UNIQUE Constraints
Read this good answer about avoid duplicates
You should do this check in the database. Always, if you want it to be true of the data.
I'm not sure what you consider a duplicate. Normally, an id column would be an identity column that is automatically incremented for each value. This would prevent duplicates. You would define it as:
create table test_table (
id int not null identity(1, 1),
. . .
Then, you would insert into it using:
insert into test_table(name)
values (#Name);
The id would be assigned automatically.
If you want no duplicates just for name, then create a unique index or unique constraint (really the same thing). You can do this in the table definition just by adding unique to the column:
create table test_table (
id int not null identity(1, 1),
name varchar(255) unique
. . .
Or by creating a unique index after you have created the table:
create index test_table_name on test_table(name)
(Or by explicitly creating a constraint, which is another method.)
In either case ,you will have to access to database to check wheteher values exist already.
IF NOT EXISTS (SELECT * FROM Test_Table WHERE ID= #ID AND Name=#Name)
BEGIN
INSERT INTO Test_Table
VALUES (#Id,#Name)
END
If it is possible to make ID column as unique you can avoid checking as insertion would.t be allowed for repeating ID values , in that case you will have to handle error.
See this thread how to handle violation of Unique key constraint.
If you don't want repeating IDs you'll have to set the ID as the Primary Key, which is pretty much obligatory.
If you don't want the Name to repeat, you could populate a list with the Names the table contains, and then you would only insert whatever name is not in that List.
Here is an example, instead of using a list I used a dictionary:
Dictionary<int, string> Names = new Dictionary<int, string> ();
using (SqlCommand command = new SqlCommand ("SELECT * FROM TestTable", con))
using (SqlDataReader reader = command.ExecuteReader ()) {
while (reader.Read ()) {
Names.Add (reader["ID"], reader["NAME"]);
}
}
if (!Names.ContainsValue ("ValueYouWantToInsert")) {
//do stuff
}
You should check it in DB, Also you can make ID as Primary Key
Which is mostly used, because people can have duplicate name.
You can modify your Id with the Unique key constraint or you can also make it Primary key.
Try like this:
alter table Test_Table add primary key (ID)
and
alter table Test_Table add unique key (Name)
IF NOT EXISTS (SELECT * FROM Test_Table WHERE ID= #ID AND Name=#Name)
BEGIN
INSERT INTO Test_Table
VALUES (#Id,#Name)
END
ELSE
BEGIN
UPDATE Test_Table
SET ID= #ID,NAME = #Name
WHERE ID= #ID AND Name=#Name
END
I have 2 tables in which i want to insert data one after another. The primary key of first table is in the 2nd. Is there any C# function so that i can insert the primary key of first table into another at 1 go, without any select query?
You can accomplish it with a stored procedure that performs both inserts and returns the identity value to the caller.
CREATE PROCEDURE procedure1
AS
BEGIN
DECLARE #id int;
INSERT INTO [table1] (col1) VALUES ('Foo');
SET #id = SCOPE_IDENTITY();
INSERT INTO [table2] (col1, col2) VALUES (#id, 'Bar');
RETURN #id;
END
You might look at using the OUTPUT clause in your insert statment.
Not sure if I understand your question but I think you want to know the primary key without consulting the server.
It this case you need to use guid's as the primary key which can be generated client side in C#. Identity columns won't work as they are generated by sql server.
Or you you could create a stored procedure that does the insert for you at the server and leave the identities at the client empty.
Update 1
To get the latest generated identity from sql server you can use
SCOPE_IDENTITY
(This is equivalent to mysql_insert_id() )
There are some other options namely
##IDENTITY
SCOPE_IDENTITY()
IDENT_CURRENT
Which you can read up on at http://blog.sqlauthority.com/2007/03/25/sql-server-identity-vs-scope_identity-vs-ident_current-retrieve-last-inserted-identity-of-record/
I have an ASP.NET application that generates GUIDs in the code-behind via C#. These GUIDs are generated via the following:
Guid id = Guid.NewGuid();
This GUID is later stored in a SQL Server 2008 database. I also have a stored procedure that will update that record. I would like to generate a GUID in the stored procedure that is in the same format as the one generated in ASP.NET.
Can somebody please tell me how to do this?
Thank you!
Use NEWID() method
DECLARE #ID uniqueidentifier
SET #ID = NEWID()
If this is for a clustered index (most often a primary key), I highly recommend NEWSEQUENTIALID() (SQL Server 2005 on up) since, NEWID() will create a fragmented index in that case, being truly random.
This will generate a GUID for you: SELECT NEWID()
Examples may be found here: http://msdn.microsoft.com/en-us/library/ms190348.aspx
My guess from the way that you have worded your question is that you are storing the GUIDs in a text (e.g. VARCHAR) field in the database - if this is the case then you should instead be using the uniqueidentifier type in which case you can use the NEWID() SQL function to generate a new GUID.
See C# guid and SQL uniqueidentifier for more detail on how to store GUIDs in an SQL Server database.
You could use NEWID().
But, there are issues with indexing guids generated like this. Instead, you should use the comb algorithm:
CAST(CAST(NEWID() AS BINARY(10)) +
CAST(GETDATE() AS BINARY(6)) AS UNIQUEIDENTIFIER)
Make sure you are storing these in a column of type UNIQUEIDENTIFIER and not converting them to NVARCHAR or anything of the sort.
You can use the NEWSEQUENTIALID for better indexing support, but the downside is that you can use this function only as a default value expression for your column.
You can use something like:
INSERT INTO MyTABLE (...) OUTPUT inserted.GUIDCOLUMN INTO #tableVar VALUES (...)
to access the newly generated sequential id.