Data Engineering Associate with Databricks Practice Exam

What does the 'Overwrite' function do in the context of Delta Lake writes?

1. Appends new records to the table

2. Deletes all existing records first

3. Completely replaces existing table data

4. Updates specific records based on conditions

The correct answer is: Completely replaces existing table data

The 'Overwrite' function in Delta Lake's context refers to completely replacing the existing table data with new data during write operations. This means that when an overwrite operation is executed, the entire content of the target table is discarded, and the new dataset is written in its place. This functionality is particularly useful when you need to refresh the entire dataset, ensuring that what is available in the table is completely up-to-date with the most recent data. This operation is distinct from appending new records, which simply adds additional data without modifying existing data. It also differs from deleting records first, as 'Overwrite' does not explicitly delete records—it replaces the entire set at once. Additionally, this function does not update specific records; rather, it replaces everything in the table, which is fundamentally different from partial updates that only change certain rows based on specified conditions. Thus, the correct choice reflects a complete overwrite of data, aligning perfectly with Delta Lake’s capabilities for managing data in a streamlined manner.