To load content from a Parquet file into a lakehouse and ensure it displays as a table, what file format must be specified in the write command?

The process of loading content from a Parquet file into a lakehouse and ensuring it displays correctly as a table specifically requires the use of the Delta format in the write command. Delta Lake extends the capabilities of the data lake by adding a layer of transactional support, which is essential for ensuring data integrity and consistency.

When data is written in the Delta format, it allows the lakehouse to leverage features like ACID transactions, scalable metadata management, and support for both batch and streaming data. This means that once the Parquet data is loaded into a Delta table, users can perform various operations such as updates, deletes, and merges seamlessly, which could be challenging with other formats such as JSON or CSV.

While Parquet is an efficient columnar storage format that provides good performance for data processing and is often used as a foundational format in data lakes, it does not encapsulate the transactional capabilities that Delta Lake offers. Thus, using Delta ensures that the data behaves like a true table with all the necessary functionalities needed for data analytics and querying in a lakehouse environment.