Partition columns for an external table can be defined using expressions such as col1 varchar as (parse_json(metadata$external_table_partition):col1::varchar). Is this statement true?

• A. Not supported
• B. Only for AWS
• C. True
• D. False

Answer: (C)

Partition columns for an external table can be created as derived columns from the partition metadata, using expressions that extract values from the file’s partition information. In Snowflake, the partition details for external data are available in a JSON structure stored in a pseudo-column called metadata$external_table_partition. By using an expression like parse_json(metadata$external_table_partition):col1::varchar, you parse that JSON, pull out the field col1, and cast it to the desired type to expose it as a column in the external table. This lets you query and filter on partition values as if they were regular columns, enabling more efficient pruning of the files Snowflake needs to scan. This approach is supported across cloud providers, not limited to AWS, and the idea is to derive the partition column from the external table’s partition metadata rather than from the data itself.