What is the purpose of valid_from and valid_to fields in dimension or fact tables?

• A. To record the last updated timestamp only.
• B. To indicate the time interval during which a row is current, enabling temporal queries and SCD Type II history.
• C. To store version numbers for software deployment.
• D. To indicate the currency of physical data files.

Answer: (B)

The idea being tested is how we track when data is in effect over time in a warehouse. valid_from and valid_to mark the time window during which a row’s attributes are considered current. This lets you answer questions like “what did this record look like on a given date?” and supports historical analysis across ranges of dates.

In practice, these fields are central to Slowly Changing Dimension Type II, where changes to a dimension aren’t overwriting the old data. Instead, a new row is inserted with a new valid_from date and a different valid_to date, preserving the earlier state for its historical period. A current row often uses a far-future date (like 9999-12-31) for valid_to to indicate it’s still in effect.

The other options don’t fit because a last_updated timestamp alone doesn’t define a time interval of validity, version numbers are about software releases rather than data validity in a table, and data file currency isn’t about the temporal state of a row within the table.