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'm creating an application that reads data from a PLC and writes it into a database.
In my GUI the user can select which data he wants to log into the database, but I'm wondering how to solve this.
sometimes the user wants to log only one item in the database :
INSERT INTO myTabel (name_data1) VALUES ("123")
but other times I must be able to choose more data :
INSERT INTO myTabel (name_data1, name_data2, name_data3) VALUES ("123", "456", "789")
how would I code this? The column names name_data1, name_data2, name_data3, ... in my database should be able to change according to which data is chosen
for this purpose I use a list of 2 strings
["name_data1", "123"],
["name_data2", "456"],
["name_data3", "789"]
so the problem also is that I do not know how the table will look like at the moment I insert the data, it all depends on which data the user chooses to be inserted into the database
If I'm correct this is called creating dynamic columns, but I do not seem to find much info on this subject.
yo can always use all the columns and if a value is not provided you pass null
like
INSERT INTO myTabel (name_data1, name_data2, name_data3) VALUES ("123", null, "789")
but if you want to use dynamic sql which is not always recommended would look like this :
DECLARE #sqlstatement as varchar(1000)= 'insert into myTabel (name_data1, name_data2, name_data3) VALUES ( #col1, #col2, #col3)'
declare #parmlist = '#col1 varchar(50) , #col2 varchar(50), #col3 varchar(50)'
exec sp_executesql
#sqlstatement
,#parmlist
, #col1 = '123'
, #col2 = NULL
, #col3 =NULL
I have 4 tables say, table1, table2, table3 and table4, which are interrelated.
Table1 will generate a primary key, that will be used in rest of the tables as reference key.
I have to insert multiple records in table 4 using this primary key.
Since the requirement is the transaction should either commit successfully or it should rollback all the changes. That is the reason I thought of writing this in stored procedure.
But got stuck, when I had to pass multiple rows data for table4.
Can anyone please suggest, how can I achieve this?
Thanks, in advance.
i guess you want to do something like this
CREATE OR REPLACE PROCEDURE myproc
(
invId IN NUMBER,
cusId IN NUMBER
)
IS
temp_id NUMBER;
BEGIN
INSERT INTO myTable (INV_ID)
VALUES (invId)
returning id into temp_id;
INSERT INTO anotherTable (ID, custID)
VALUES (temp_id, custId);
END myproc;
I'm doing some web scraping to build up a personal SQL database. As I'm looping through the web requests, I'm adding records. The only thing is, duplicates sometimes appear in the web requests and I want to make sure to only add a record if it doesn't already exist in my database. I gather this can be done by performing an SQL query before every insert to make sure that record hasn't already been added, but is this the best way to do it? Would it make more sense to build up a Generic.List first, and then do all my database inserts at the end?
You can create a stored procedure that will attempt to update a record and then insert if the update query did not update any rows. This will minimize the number of queries that need to be run and prevent checking for the row's existence. A little bit of Googling found this. The second option looks like it might be what you are looking for.
/*
Same SP is used to INSERT as well as UPDATE a table.
Here we are avoid unnecessary checking of whether the record exists or not.
Instead try to Update directly. If there is no record then ##RowCount would be 0.
Based on that Insert it as a new record.
*/
CREATE PROCEDURE uspUPSert_Ver2
(
#empID INT,
#fname VARCHAR(25),
#lname VARCHAR(25),
#emailid VARCHAR(50)
)
AS
BEGIN
SET NOCOUNT ON
BEGIN TRAN
UPDATE tblUpsert WITH (SERIALIZABLE)
SET emailid = #emailid ,
firstname = #fname ,
lastname = #lname
WHERE EmpID = #empID
IF ##ROWCOUNT = 0
BEGIN
INSERT INTO tblUpsert VALUES (#empID, #fname, #lname, #emailid)
END
COMMIT TRAN
END
GO
seems like you would need either a primary key or a unique constraint on the columns that identify the rows as duplicate. Then if there is an error in the insert that violates the unique constraint the row won't insert. Catch the exception, log it to a different table for future validation and move to the next row.
http://www.w3schools.com/sql/sql_unique.asp
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/