Nov 22, 2018  It generates auto-incrementing values in table by defining seed and increment values, works much like SEQUENCE object in SQL Server and Oracle. However, IDENTITY property is table dependent and SEQUENCE object works independently from the table. Often we require to get last identity inserted value in SQL server. Multiple functions and methods. Create Primary Keys.; 2 minutes to read +6; In this article. APPLIES TO: SQL Server 2016 and later Azure SQL Database Azure Synapse Analytics (SQL DW) Parallel Data Warehouse You can define a primary key in SQL Server by using SQL Server Management Studio or Transact-SQL. I have inserted records into a SQL Server database table. The table had a primary key defined and the auto increment identity seed is set to “Yes”. This is done primarily because in SQL Azure, each table has to have a primary key and identity defined. AUTO INCREMENT Field. Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table. Often this is the primary key field that we would like to be created automatically every time a new record is inserted. Sep 14, 2017 In Entity Framework 6 you can create an entity and set the primary key property to whatever value you want, because in case the ID is generated in database (i.e. Identity in MS SQL Server) the value will be overwritten anyway. And Entity Framework 6 will happily work with that scenario.

  1. Update Auto Generated Primary Key Sql Server Set Identity_insert Windows 10
  2. Update Auto Generated Primary Key Sql Server Set Identity_insertt Off
  3. Update Auto Generated Primary Key Sql Server Set Identity_insertt
  4. Update Auto Generated Primary Key Sql Server Set Identity_insert Sert Off
By: Ben Richardson Updated: 2018-09-26 Comments (6) Related: More >Identities

Problem

While designing a SQL Server database, the primary key column is often set to auto-increment. To do this, the IDENTITY constraint is set on the primary key column. The starting position and the increment step are passed as parameters to the IDENTITY column. Then whenever a new record is inserted, the value of the IDENTITY column is incremented by the pre-defined step, usually a number. Now if a record is deleted, the IDENTITY column value for that record is also deleted. If a new record is inserted, its value for the IDENTITY column will be incremented from the previous figure in the column. It is not possible to reuse the value that was originally used by the now deleted record. If you try to specify the value for the IDENTITY column, an error will be thrown. So how do you reuse the value that was assigned to the deleted record?

Solution

The solution to this problem is to switch on the SET IDENTITY INSERT flag, which is off by default. Switching the SET IDENTITY INSERT flag to ON allows for the insertion of any random value to the IDENTITY column, as long as it doesn't already exist.

In this article, I will explain (with the help of an example) how to insert a missing value into the IDENTITY column.

Setup Example Table and Data

First let’s create some dummy data. We will execute our sample queries on this new database.

In the script, we create a dummy database “School”. Next, we execute the script that creates a table named “Students”. If you look at the table design, you can see that it contains three columns Id, StudentName and StudentAge. The Id column is the primary key column with an IDENTITY constraint. Both the seed and step values for IDENTITY are set to 2. This means that the first record in the “Students” database will have the Id value of 2 and each subsequent record will have a value incremented by 2. Finally, we insert 5 random records into the Students table.

Now if you select all the records from the Students table, you will see that Id column will contain a sequence of values starting at 2 and incremented by 2 in each row. Execute the following script:

The output looks like this:

You can see that the first record has an id value of 2 while the 5th has a value of 10.

Now, suppose one of the students leaves the school and we want to delete his record. We can do so using a simple DELETE statement. Let’s delete the record of Jon:

Now if you again look at all the records in the Students table using SELECT statement, you will see the following output:

You can see from the output that record of the student “Jon” with Id 6 has been deleted.

Now let’s try to insert a record of a new student and see what Id it gets:

The above script inserts a record of a new student named “Jessica”, aged 27, to the Students table.

To see the Id assigned to the Jessica, again retrieve all records from the Students table using the SELECT statement as shown below:

The output looks like this:

You can see from the output that Jessica has been assigned the Id 12 instead of the Id 6 vacated by Jon. The reason for this behavior is the fact that by default IDENTITY column assigns a value to a new record by adding the step to previous maximum value in the column instead of filling the vacant values in the column. Since the previous maximum value in the Id column was 10, therefore Jessica is assigned 12, since the step is 2.

Update Auto Generated Primary Key Sql Server Set Identity_insert Windows 10

Depending upon the business rules of the application being developed, this behavior can be correct. For instance, a School may have a rule that even if a student leaves the school, his/her Id cannot be assigned to a new student. On the other hand, there can be a school that reassigns the Id of a student who leaves the school, to a new student.

Manually Insert Record with specific ID value

Update auto generated primary key sql server set identity_insertt on

Update Auto Generated Primary Key Sql Server Set Identity_insertt Off

In the latter case, one of the solutions is to manually insert the Id value for the new student.

Let’s try to add a record of a new student and manually set the value for the Id column to 6 as shown below:

The above script inserts a record of a new student named “Nick”, aged 22, and Id 6, to the students table. When you try to execute the above script, an error will be thrown which looks likes this:

Msg 8101, Level 16, State 1, Line 26
An explicit value for the identity column in table 'Students' can only be specified when a column list is used and IDENTITY_INSERT is ON.

In simple words, the error says that since the flag IDENTITY_INSERT is off for the Id column, we cannot manually insert any values. Another important consideration is that we need to specify the column names as well while inserting data to IDENTITY column.

If we try to just specify the column names as mentioned in the above error message as follows:

We get this error message.

Msg 544, Level 16, State 1, Line 35
Cannot insert explicit value for identity column in table 'Students' when IDENTITY_INSERT is set to OFF.

To manually insert a new value into the Id column, we first must set the IDENTITY_INSERT flag ON as follows:

To set the IDENTIT_INSERT flag ON we need to use the SET statement followed by the flag name and the name of the table.

Now if we again try to insert the record of the student “Nick” with Id 6, no error will be thrown. Execute the following statement again:

You can see that we have specified the name of the columns as well for inserting a record.

Now again use SELECT statement to retrieve all records from students table in order to view if our new record has been inserted or not. The SELECT statement will return the following records.

You can see from the output that record of a new student named “Nick”, aged 22, and Id 6 has been inserted to the Students table.

Try Inserting Duplicate Values

If we try to insert duplicate values as follows:

We will get this error, since ID is the primary key for the table which has to be a unique value.

Msg 2627, Level 14, State 1, Line 35
Violation of PRIMARY KEY constraint 'PK__Students__3214EC071AD8EC3F'. Cannot insert duplicate key in object 'dbo.Students'. The duplicate key value is (6).
The statement has been terminated.

Note, that if the ID column was not a Primary Key we would be able to insert duplicate records.

Turn IDENTITY INSERT off

When you SET INDENTITY_INSERT ON it will stay on for the entire session (the time the query window is open). So once this is set you can insert as many records as you want. Also, this only applies for the session where this is turned on, so if you open another query window you would need to set this ON for that query window.

To turn off this option for the session, you would issue the following statement.

Next Steps
  • In this article, we saw that how we can use the SET IDENTITY_INSERT flag as ON in order to insert a record in the IDENTITY column which is not possible with default settings.
  • Check out these related articles:

Last Updated: 2018-09-26



About the author
Ben is the owner of Acuity Training, a UK based IT training business offering SQL training up to advanced administration courses.
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Posted August 15, 2019 by Vishwanath Dalvi in Database, SQL Server

SQL Server includes IDENTITY property to generate auto-increment numbers. IDENTITY generates incrementing numbers when a record is inserted into a table. Often referred to as a surrogate key, and commonly used as a primary key to have unique incrementing values in a column. While inserting a record in a table, we do not have to specify identity value explicitly, as by default it takes the next value.

IDENTITY( Seed, Increment)

IDENTITY property takes Seed & Increment as arguments to specify the starting number and incremental gap to the next number. For example, IDENTITY (1,1) specifies that the column value will start at 1 and always incremented by adding 1 to the previous value.

This example will create a Monk table with an Identity column. As a rule, without explicitly specifying ID column we have incremental numbers using IDENTITY property.

Example



SET IDENTITY_INSERT [DBName.SchemaName.TableName] ON/OFF

Presumably, in a scenario, we might need to explicitly add values in the IDENTITY type column. SQL Server included this as an option with IDENTITY_INSERT property. Let’s consider we have done a lot of delete operations on a table. Due to this, the identity column has many gaps. To fill these gaps, we are explicitly adding values to the identity type column.

Syntax


DbName – In case applying this property to different database. Although optional if you are in the same database.

SchemaName – If table has got schema other than dbo then mandatory to specify this parameter.

TableName – Mandatory to specify this parameter to give name of table with an identity column.

Example

In this example, reusing the previous query. Populating Monk table with 1 to 10 values in the Identity type column. Later deleting values from 3 to 6 thus creating a gap in the Identity column. If we directly try to insert value 3 in identity column then SQL Server will raise an error.



Use SET IDENTITY_INSERT [TableName] ON

To avoid error while inserting explicit value in a table using IDENTITY_INSERT property. We need to wrap Insert statement within IDENTITY_INSERT ON & OFF. Following this, we can easily insert explicit values in the identity type column.

Referring to the rule, we can have only one IDENTITY_INSERT property set to on in a session. In short, If we have set IDENTITY_INSERT ON for a table then we can not use the same property on another table. Until we have turned OFF the previous property. This can result in an error.

Update Auto Generated Primary Key Sql Server Set Identity_insertt

In the following query, we are successfully able to insert values in Monk table using IDENTITY_INSERT ON property.


Forcing Explicit Value Without IDENTITY_ON Property

If we run the following query, we will get an error stating explicit values for identity columns are not allowed unless we specify IDENTITY_INSERT property to ON.


Msg 544, Level 16, State 1, Line 25
Cannot insert explicit value for identity column in table ‘Monk’ when IDENTITY_INSERT is set to OFF.


IDENTITY_INSERT – Single Per Session

In contrast to the use of IDENTITY_INSERT property allowed once per table in a session. If you try to turn ON this property for multiple tables at the same time SQL Server raises an error. In this query, trying to use this property on multiple tables resulted in an error.


Update Auto Generated Primary Key Sql Server Set Identity_insert Sert Off


Summary

As a result, we have learnt to use IDENTITY_INSERT ON/OFF property. Using this we can explictly insert values to fill the gaps in Identity type column. If you like this post, you may want to explore more on Tech-Recipes Database Archive posts to learn more useful stuff.

About Vishwanath Dalvi

Vishwanath Dalvi is a gifted engineer and tech enthusiast. He enjoys music, magic, movies, and gaming. When not hacking around or supporting the open source community, he is trying to overcome his phobia of dogs.
View more articles by Vishwanath Dalvi

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