Database: Change Data Capture (CDC)

Change Data Capture (CDC) is a technique used in databases to track and capture changes made to the data. It allows you to capture insert, update, and delete operations on the data in real-time. CDC is essential for maintaining data integrity, auditing data changes, and replicating data across multiple systems efficiently.

How CDC Works

CDC works by capturing the changes made to the database tables and storing them in a separate log or table. This log contains information about the type of operation (insert, update, delete), the affected columns, and the old and new values. By reading this log, applications can track changes and react accordingly.

Code Snippet: CDC Implementation in SQL Server

```sql -- Enable CDC on a Database EXEC sys.sp_cdc_enable_db; -- Enable CDC on a Table EXEC sys.sp_cdc_enable_table @source_schema = 'dbo', @source_name = 'MyTable', @role_name = NULL; ```

Example: CDC Output

Let's consider a scenario where we have a table Employees with columns EmployeeID, FirstName, and LastName. If a new employee is added to the table, the CDC log will capture the insert operation along with the employee details.

CDC Log Output:

Operation	EmployeeID	FirstName	LastName
INSERT	101	John	Doe

Common Use Cases

CDC is commonly used for data replication, auditing, data synchronization, and tracking data changes for compliance purposes. It is also useful in scenarios where you need to maintain a history of changes to the data.

Importance of CDC in Interviews

CDC is a fundamental concept in database management and is frequently asked about in interviews for database administrator and developer roles. Understanding CDC demonstrates your knowledge of data integrity, data tracking, and database optimization.

Conclusion

Change Data Capture (CDC) is a crucial technique in database management that allows you to track and capture changes made to the data. By implementing CDC, you can ensure data integrity, audit data changes, and replicate data efficiently across multiple systems.

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