How to Enable and Disable IDENTITY_INSERT in SQL Server 2008 for Controlled Identity Column Insertions?

SQL Server 2008: Managing Identity Column Inserts Using IDENTITY_INSERT

In SQL Server databases, situations arise where you need to manually insert values into identity columns. However, IDENTITY_INSERT is disabled by default, preventing direct insertion.

Understanding the IDENTITY_INSERT OFF Error

Attempting to insert a value into an identity column with IDENTITY_INSERT set to OFF results in this error:

Cannot insert explicit value for identity column in table 'TableName' when IDENTITY_INSERT is set to OFF.

This is because SQL Server automatically manages unique identity values. When IDENTITY_INSERT is OFF, the database expects the identity column to be empty, allowing it to assign the next sequential value.

Enabling IDENTITY_INSERT using SQL Server Management Studio (SSMS)

To enable IDENTITY_INSERT for a specific table in SSMS:

1. Right-click the database containing the target table.
2. Choose "New Query".
3. Execute the following T-SQL command, replacing <tablename> with your table's name:

SET IDENTITY_INSERT <tablename> ON;

4. After execution, insert your data. Remember to disable IDENTITY_INSERT afterwards.

Using T-SQL Directly

You can also manage IDENTITY_INSERT directly within T-SQL:

SET IDENTITY_INSERT sometableWithIdentity ON;

INSERT INTO sometableWithIdentity (IdentityColumn, col2, col3, ...)
VALUES (AnIdentityValue, col2value, col3value, ...);

SET IDENTITY_INSERT sometableWithIdentity OFF;

Detailed Error Messages

Error messages will specify the affected table, aiding in problem identification. For example:

<code>Cannot insert explicit value for identity column in table 'Baskets' when IDENTITY_INSERT is set to OFF.</code>

By temporarily enabling IDENTITY_INSERT, you control identity column values. Always disable it afterward to maintain database integrity and sequential identity generation.

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