Why Does SQL Throw a 'Cannot Insert Explicit Value for Identity Column' Error and How Can I Fix It?

Troubleshooting the "Cannot Insert Explicit Value for Identity Column" SQL Error

Encountering the error "Cannot insert explicit value for identity column in table 'table' when IDENTITY_INSERT is set to OFF" during SQL insert operations? This guide explains the cause and provides a solution. This error occurs when you attempt to manually assign a value to a column designated as an identity column, which automatically generates values.

Understanding Identity Columns in SQL

Identity columns are database columns that automatically increment, usually serving as primary keys or unique identifiers. The database manages the incrementing process, typically adding a fixed step value (often 1) for each new row. This ensures unique, sequential values, vital for database operations and referential integrity.

Root Cause of the Error

The error arises from attempting to insert a value directly into an identity column while the table's IDENTITY_INSERT property is set to OFF. This setting prevents manual value assignments to identity columns.

Resolving the Error: Enabling and Disabling IDENTITY_INSERT

The solution involves temporarily enabling IDENTITY_INSERT for the affected table to permit manual insertion. Here's the process:

1. Enable IDENTITY_INSERT: Execute the following command, replacing [TableName] with your table's name:

   SET IDENTITY_INSERT [TableName] ON

2. Perform the Insert: Now, execute your insert statement with the explicit value for the identity column.

3. Disable IDENTITY_INSERT: After the insertion, immediately disable IDENTITY_INSERT to restore the automatic generation behavior:

   SET IDENTITY_INSERT [TableName] OFF

This ensures that subsequent inserts will again use the automatic increment feature for the identity column, maintaining the integrity of your database. Remember to always disable IDENTITY_INSERT after each manual insertion to prevent unexpected behavior.

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