1. Performance: Clickhouse is designed specifically for analytic workloads and offers extremely high performance for querying large amounts of data. It utilizes a columnar storage format and highly optimized data compression techniques, which allows for efficient data retrieval. On the other hand, MemSQL is an in-memory database that emphasizes real-time processing and high throughput. It stores data in memory for faster access, making it well-suited for applications that require low latency.
2. Scale: Clickhouse is designed to handle petabytes of data and can efficiently store and process large datasets across multiple servers. It supports scalable distributed query execution and can be easily scaled horizontally by adding more servers to the cluster. MemSQL also offers scalable capabilities but is primarily focused on scaling horizontally and provides strong consistency across all nodes in the cluster.
3. Data Consistency: Clickhouse supports eventual consistency, which means that updates to the data may not be immediately reflected in all replicas, but eventually, they will be consistent. MemSQL, on the other hand, provides strong consistency guarantees, ensuring that all updates are immediately reflected across the entire cluster.
4. SQL Compatibility: Clickhouse supports a subset of SQL and provides extensions for analytical queries. It also supports the standard SQL DDL statements for managing tables. MemSQL is fully SQL compatible and supports a wide range of SQL features, making it easier for developers to migrate existing applications to MemSQL.
5. Data Durability: Clickhouse focuses on performance and efficiency, and as such, it does not provide built-in replication or fault tolerance mechanisms. However, it supports integrating with external replication solutions. MemSQL, on the other hand, provides built-in replication and fault tolerance mechanisms to ensure data durability and high availability.
6. Data Storage: Clickhouse stores data in a columnar format, which is optimized for analytical queries. It compresses data to reduce storage requirements and utilizes efficient indexing techniques for faster data retrieval. MemSQL stores data in memory, allowing for faster read and write operations. It also supports persistent disk storage for durability.

In Summary, Clickhouse is optimized for analytical workloads, offers efficient data retrieval with columnar storage, and supports eventual consistency. MemSQL focuses on real-time processing with in-memory storage, strong consistency, and provides built-in replication and fault tolerance mechanisms.