I would like to change increment value of IDENTITY column in database and I have below restrictions:
Can't drop the column.
Having around 20k rows.
Dropping table and recreate table with changed increment value would be the solution. I don't know the syntax.
Can you please suggest the syntax or other best possible solution?
Thanks in Advance!
If i understand you correctly base on your response to my comment, you backed up the data of the orig table in temp table, then you deleted the orig table and you want to recreate an orig table.
If that is the case , you need the IDENTITY_INSERT to set ON and OFF, because the identity of the table is unique.
The syntax is:
SET IDENTITY_INSERT [TableName] ON -- set to on
-- Put your insert statement here
-- insert the data from backed up temp table to your new table
SET IDENTITY_INSERT [TableName] OFF -- set to off
If you can accept recreating table, there is no magic about the recreating table syntax.
CREATE TABLE temp_Table
(
-- Identity column with new settings
-- other columns
);
INSERT INTO temp_Table
SELECT -- Columns except identity column
FROM old_table;
DROP TABLE old_Table;
EXEC sp_rename 'temp_Table', 'old_Table';
However, you have to handle foreign key by yourself.
Altering identity column after table creation is not possible.
Instead, reset SEED value using the below command.
DBCC CHECKIDENT('tablename', RESEED, 15)
I have a database in which all the tables have column named ID. I need to alter all tables in database and add identity to these columns. Is it possible with some query ? Or do I have to do it manually?
Thank you very much.
Unfortunately in SQL Server you cannot add identity property to existing columns. You need to drop an existing one, then create new with this property. You can automate this task by quering system tables and using dynamic sql. But if you already have some data in ID column this will make things more tricky because you need to preserve existing data.
Here is a script for a single table, automating this for all tables in database using dynamic sql will be kinda tricky...
Table Test_table has 2 columns: id and val.
-- Move data to temp storage
SELECT ID,
VAL
INTO #temp_table
FROM dbo.test_table
-- Remove data from original table
DELETE
FROM dbo.test_table
-- Drop and Create ID column
ALTER TABLE dbo.test_table
DROP COLUMN ID
ALTER TABLE dbo.test_table
ADD ID int IDENTITY(1,1)
-- Move data back to original table
SET IDENTITY_INSERT dbo.test_table ON
INSERT INTO dbo.test_table (ID, VAL)
SELECT ID, VAL
FROM #temp_table
DECLARE #MaxID int
SELECT #MaxID = MAX(ID) + 1
FROM dbo.test_table
SET IDENTITY_INSERT dbo.test_table OFF
-- Reseed IDENTITY property
DBCC CHECKIDENT ('dbo.test_table', RESEED, #MaxID)
There is no way to do this for all tables. Here's what I'd do: Use T-SQL to generate a (big) script that performs all the changes, then manually run that script.
You can add the identity property to existing columns without data movement using SWITCH.
We consume a web service that decided to alter the max length of a field from 255. We have a legacy vendor table on our end that is still capped at 255. We are hoping to use a trigger to address this issue temporarily until we can implement a more business-friendly solution in our next iteration.
Here's what I started with:
CREATE TRIGGER [mySchema].[TruncDescription]
ON [mySchema].[myTable]
INSTEAD OF INSERT
AS
BEGIN
SET NOCOUNT ON;
INSERT INTO [mySchema].[myTable]
SELECT SubType, type, substring(description, 1, 255)
FROM inserted
END
However, when I try to insert on myTable, I get the error:
String or binary data would be
truncated. The statement has been
terminated.
I tried experimenting with SET ANSI_WARNINGS OFF which allowed the query to work but then simply didn't insert any data into the description column.
Is there any way to use a trigger to truncate the too-long data or is there another alternative that I can use until a more eloquent solution can be designed? We are fairly limited in table modifications (i.e. we can't) because it's a vendor table, and we don't control the web service we're consuming so we can't ask them to fix it either. Any help would be appreciated.
The error cannot be avoided because the error is happening when the inserted table is populated.
From the documentation:
http://msdn.microsoft.com/en-us/library/ms191300.aspx
"The format of the inserted and deleted tables is the same as the format of the table on which the INSTEAD OF trigger is defined. Each column in the inserted and deleted tables maps directly to a column in the base table."
The only really "clever" idea I can think of is to take advantage of schemas and the default schema used by a login. If you can get the login that the web service is using to reference another table, you can increase the column size on that table and use the INSTEAD OF INSERT trigger to perform the INSERT into the vendor table. A variation of this is to create the table in a different database and set the default database for the web service login.
CREATE TRIGGER [myDB].[mySchema].[TruncDescription]
ON [myDB].[mySchema].[myTable]
INSTEAD OF INSERT
AS
BEGIN
SET NOCOUNT ON;
INSERT INTO [VendorDB].[VendorSchema].[VendorTable]
SELECT SubType, type, substring(description, 1, 255)
FROM inserted
END
With this setup everything works OK for me.
Not to state the obvious but are you sure there is data in the description field when you are testing? It is possible they change one of the other fields you are inserting as well and maybe one of those is throwing the error?
CREATE TABLE [dbo].[DataPlay](
[Data] [nvarchar](255) NULL
) ON [PRIMARY]
GO
and a trigger like this
Create TRIGGER updT ON DataPlay
Instead of Insert
AS
BEGIN
SET NOCOUNT ON;
INSERT INTO [tempdb].[dbo].[DataPlay]
([Data])
(Select substring(Data, 1, 255) from inserted)
END
GO
then inserting with
Declare #d as nvarchar(max)
Select #d = REPLICATE('a', 500)
SET ANSI_WARNINGS OFF
INSERT INTO [tempdb].[dbo].[DataPlay]
([Data])
VALUES
(#d)
GO
I am unable to reproduce this issue on SQL 2008 R2 using:
Declare #table table ( fielda varchar(10) )
Insert Into #table ( fielda )
Values ( Substring('12345678901234567890', 1, 10) )
Please make sure that your field is really defined as varchar(255).
I also strongly suggest you use an Insert statement with an explicit field list. While your Insert is syntactically correct, you really should be using an explicit field list (like in my sample). The problem is when you don't specify a field list you are at the mercy of SQL and the table definition for the field order. When you do use a field list you can change the order of the fields in the table (or add new fields in the middle) and not care about your insert statements.
OK, I have a table with no natural key, only an integer identity column as it's primary key. I'd like to insert and retrieve the identity value, but also use a trigger to ensure that certain fields are always set. Originally, the design was to use instead of insert triggers, but that breaks scope_identity. The output clause on the insert statement is also broken by the instead of insert trigger. So, I've come up with an alternate plan and would like to know if there is anything obviously wrong with what I intend to do:
begin contrived example:
CREATE TABLE [dbo].[TestData] (
[TestId] [int] IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Name] [nchar](10) NOT NULL)
CREATE TABLE [dbo].[TestDataModInfo](
[TestId] [int] PRIMARY KEY NOT NULL,
[RowCreateDate] [datetime] NOT NULL)
ALTER TABLE [dbo].[TestDataModInfo] WITH CHECK ADD CONSTRAINT
[FK_TestDataModInfo_TestData] FOREIGN KEY([TestId])
REFERENCES [dbo].[TestData] ([TestId]) ON DELETE CASCADE
CREATE TRIGGER [dbo].[TestData$AfterInsert]
ON [dbo].[TestData]
AFTER INSERT
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
INSERT INTO [dbo].[TestDataModInfo]
([TestId],
[RowCreateDate])
SELECT
[TestId],
current_timestamp
FROM inserted
-- Insert statements for trigger here
END
End contrived example.
No, I'm not doing this for one little date field - it's just an example.
The fields that I want to ensure are set have been moved to a separate table (in TestDataModInfo) and the trigger ensures that it's updated. This works, it allows me to use scope_identity() after inserts, and appears to be safe (if my after trigger fails, my insert fails). Is this bad design, and if so, why?
As you mentioned, SCOPE_IDENTITY is designed for this situation. It's not affected by AFTER trigger code, unlike ##IDENTITY.
Apart from using stored procs, this is OK.
I use AFTER triggers for auditing because they are convenient... that is, write to another table in my trigger.
Edit: SCOPE_IDENTITY and parallelism in SQL Server 2005 cam have a problem
HAve you tried using OUTPUT to get the value back instead?
Have you tried using:
SELECT scope_identity();
http://wiki.alphasoftware.com/Scope_Identity+in+SQL+Server+with+nested+and+INSTEAD+OF+triggers
You can use an INSTEAD OF trigger just fine, by in the trigger capturing the value just after the insert to the main table, then spoofing the Scope_Identity() into ##Identity at the end of the trigger:
-- Inside of trigger
SET NOCOUNT ON;
INSERT dbo.YourTable VALUES(blah, blah, blah);
SET #YourTableID = Scope_Identity();
-- ... other DML that inserts to another identity-bearing table
-- Last statement in trigger
SELECT YourTableID INTO #Trash FROM dbo.YourTable WHERE YourTableID = #YourTableID;
Or, here's an alternate final statement that doesn't use any reads, but may cause permission issues if the executing user doesn't have rights (though there are solutions to this).
SET #SQL =
'SELECT identity(smallint, ' + Str(#YourTableID) + ', 1) YourTableID INTO #Trash';
EXEC (#SQL);
Note that Scope_Identity() may return NULL on a table with an INSTEAD OF trigger on it in some cases, even if you use this spoofing method. But you can at least get the value using ##Identity. This can make MS Access ADP projects start working right again after breaking because you put a trigger on a table that the front end inserts to.
Also, be aware that any parallelism at all can make ##Identity and Scope_Identity() return incorrect values—so use OPTION (MAXDOP 1) or TOP 1 or a single-row VALUES clause to defeat this problem.
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: đź•—
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')