What is the least expensive data store when you only need to store data without querying it?

The least expensive data store for simply storing data without the need for querying is Azure Storage. This service is designed to provide cost-effective and durable storage solutions for a variety of data types, whether structured, semi-structured, or unstructured.

Azure Storage is particularly optimized for scalability and availability, making it an ideal choice for scenarios where data may need to be stored for later processing but does not require immediate or frequent access through complex queries. There are different types of storage options within Azure Storage, such as Blob storage for unstructured data, which allows for low-cost bulk storage solutions.

In contrast, the other options involve added capabilities that typically incur higher costs. Azure Stream Analytics specializes in real-time data processing and analytics; therefore, it is not a straightforward storage solution. Azure Databricks is a powerful analytics platform that is intended for large-scale analytics and machine learning, which requires a more involved setup and operational costs. Azure SQL Database, while providing structured data storage and querying capabilities, also involves costs associated with compute resources and storage management.

Thus, when storage needs are simple and cost-efficiency is paramount, Azure Storage offers the best solution.