SQL Server Identity Insert

The `IDENTITY` property in SQL Server automatically generates unique integer values for columns. This is a powerful feature for creating primary keys and ensuring data integrity. However, sometimes you need to insert data into a table where the identity column already has values. This is where `IDENTITY_INSERT` comes in handy. It temporarily suspends the automatic generation of identity values for a specific table. This allows you to insert values into the identity column, which would otherwise be generated automatically. It's important to note that `IDENTITY_INSERT` is a table-level operation, meaning it affects all rows inserted into the table until you turn it off again. This is a crucial aspect to understand for maintaining data integrity and avoiding unexpected results.Imagine you have a table called `Customers` with an `CustomerID` column that's set as an identity column. If you need to load data from an external source that already contains `CustomerID` values, you can use `IDENTITY_INSERT` to insert those values without conflicts. This is a common scenario when migrating data or loading initial data into a database.Using `IDENTITY_INSERT` is not a permanent solution. It's crucial to turn it off after you've inserted the necessary data to resume the automatic generation of identity values. Failure to do so can lead to unexpected behavior and data inconsistencies in subsequent inserts.In summary, `IDENTITY_INSERT` is a temporary override of the identity column's auto-incrementing behavior. It's a valuable tool for specific data loading scenarios, but it's essential to use it judiciously and remember to turn it off when you're done.