Understanding SQL Server Set Identity_Insert

Greetings, Dev! In this article, we will delve into the concept of SQL Server Set Identity_Insert. This is a powerful tool in SQL Server that allows you to insert explicit values into an identity column. We will go through its definition, syntax, and usage. We will also provide you with some useful tips and tricks. So, let’s get started!

What is SQL Server Set Identity_Insert?

SQL Server Set Identity_Insert is a command that enables you to insert explicit values into identity columns. An identity column is a numeric column that automatically generates values. It is often used as a primary key in tables. By default, you cannot insert values into an identity column. However, with Set Identity_Insert, you can override this behavior.

The Syntax of SQL Server Set Identity_Insert

The syntax of SQL Server Set Identity_Insert is simple. Here is an example:

As you can see, the syntax is very straightforward. You need to specify the table name and turn the identity insert on or off.

How to Use SQL Server Set Identity_Insert

Using SQL Server Set Identity_Insert is relatively easy. Here are the steps:

Step 1: Identify the Table and the Column

The first step is to identify the table and the identity column that you want to insert explicit values into. For example, let’s say we have a table named “Customers” with an identity column named “CustomerID”.

Step 2: Enable Identity Insert

The next step is to enable identity insert for the “Customers” table:

SET IDENTITY_INSERT Customers ON;

Once you have enabled identity insert, you can now insert explicit values into the “CustomerID” column:

INSERT INTO Customers (CustomerID, CustomerName) VALUES (1, 'John Smith');

Step 3: Disable Identity Insert

After you have inserted the explicit values, you should disable identity insert:

SET IDENTITY_INSERT Customers OFF;

That’s it! You have now successfully inserted explicit values into an identity column.

Benefits and Drawbacks of SQL Server Set Identity_Insert

Like any other tool, SQL Server Set Identity_Insert has its benefits and drawbacks. Here are some of them:

Benefits

• You can insert explicit values into an identity column, which may come in handy in certain scenarios.
• It allows you to preserve existing identities when importing data into a table.

Drawbacks

• It is not recommended to use SQL Server Set Identity_Insert frequently, as it can lead to data inconsistencies.
• Explicitly inserting values into an identity column can cause identity collisions if the values you insert already exist in the table.

Frequently Asked Questions (FAQ) about SQL Server Set Identity_Insert

Q: Can I insert explicit values into multiple identity columns in the same table?

A: No, you cannot. SQL Server Set Identity_Insert only works for one identity column at a time. You will need to repeat the process for each identity column.

Q: Can I insert explicit values into an identity column that is also a primary key?

A: Yes, you can. However, you need to ensure that the explicit values you insert are unique.

Q: Can I insert explicit values into an identity column that has a foreign key constraint?

A: Yes, you can. However, you need to ensure that the explicit values you insert exist in the referenced table.

Q: Can I use SQL Server Set Identity_Insert in a transaction?

A: Yes, you can. However, you need to ensure that you commit the transaction before disabling identity insert.

Q: How can I check if identity insert is enabled for a table?

A: You can check the current identity insert status for a table by using the following query:

SELECT OBJECTPROPERTY(OBJECT_ID('table_name'), 'TableHasIdentity')

Conclusion

In conclusion, SQL Server Set Identity_Insert is a powerful tool that can come in handy in certain scenarios. It enables you to insert explicit values into identity columns, which can be useful for preserving existing identities or importing data into tables. However, you need to use it with caution, as it can lead to data inconsistencies. We hope that this article has provided you with a better understanding of SQL Server Set Identity_Insert. If you have any questions or comments, feel free to leave them below.