Data classification in Snowflake is a feature that allows organizations to identify and categorize data stored in tables or columns based on its sensitivity level or content type. This feature can be used to find sensitive data within the database by classifying data as confidential, personal, public, etc., making it easier to apply appropriate security measures, such as masking policies or row-level security, to protect sensitive information.
References:
* Snowflake Documentation: Data Classification

In Snowflake, semi-structured data is optimally stored using specific data types that are designed to handle the flexibility and complexity of such data. The VARIANT data type can store structured and semi-structured data types, including JSON, Avro, ORC, Parquet, or XML, in a single column. The ARRAY data type, on the other hand, is suitable for storing ordered sequences of elements, which can be particularly useful for semi-structured data types like JSON arrays. These data types provide the necessary flexibility to store and query semi-structured data efficiently in Snowflake.
References:
* Snowflake Documentation: Semi-structured Data Types

Reference: https://community.snowflake.com/s/article/Making-Transient-table-by-Default