Which ALTER TABLE command can change a column's data type, potentially impacting Time Travel behavior?

• A. ALTER TABLE ... SET NOT NULL ...
• B. ALTER TABLE ... DROP COLUMN ...
• C. ALTER TABLE ... RENAME COLUMN ...
• D. ALTER TABLE ... SET DATA TYPE ...

Answer: (D)

Changing a column’s data type tests your understanding of how data representation and interpretation can evolve over time. In Snowflake, you alter the column to set a new data type, which converts the existing values to that type. This operation directly changes how data is stored and read going forward, and if the conversion isn’t possible for some values, the change will fail.

Time Travel looks at data as it existed at a past moment, including how that data was stored then. When you change a column’s type, historical snapshots remain with the old representation, while newer data uses the new type, so the way values are interpreted can differ between points in time. Because of this, a data type change can impact how Time Travel presents historical data compared with after the change.

The other actions modify constraints, remove a column, or rename a column, none of which reconfigure how the actual data is stored at the type level, so they don’t affect Time Travel in the same way.