rsql.ch

What It Is

RSQL Server is a lightweight, simplified alternative to Microsoft SQL Server. Its goal is to implement basic T-SQL commands so that some C# applications can run without purchasing expensive SQL Server licenses. It is written in Go, licensed under GPL v3, supports Linux and Windows, and emphasizes full Unicode support, multi-user access, ACID compliance, and transaction capabilities.

Core Features and Ecosystem

In terms of functionality, RSQL is more of a “basic T-SQL database server” than a full SQL Server clone. It supports core operations such as INSERT, UPDATE, DELETE, and SELECT, uses table-level read/write locks, and relies on journal files to maintain transaction consistency in the event of a crash or power failure. Each table and index is stored as a separate file, and it can manage millions of records.

Currently, only a C# driver is available. Its usage is close to the native SQL Server driver, and the documentation claims that switching between RSQL and MS SQL Server requires changing just one line of code. Ecosystem-wise, it mainly serves the Microsoft/C# stack. A JDBC driver is planned, but has not yet been implemented.

Pricing and Open Source

RSQL’s biggest appeal is that it is free and open source under GPL v3. For small and midsize businesses under pressure from SQL Server licensing based on hardware capacity or core counts, it may reduce licensing costs by thousands to tens of thousands of dollars in basic use cases. It also allows multiple instances to be deployed across multiple machines without commercial licensing restrictions.

Pros and Cons

Its strengths are clear positioning, a low learning curve, support for self-hosting, the ability to run on Linux and Windows, and retention of core database requirements such as transactions and ACID. The drawbacks are also significant: it only implements a subset of T-SQL and does not support common features such as stored procedures, views, triggers, subqueries, CHECK constraints, system views, or DESC sorting. The optimizer does not currently reorder tables in the FROM clause, so complex queries require manual tuning. At present, the only driver is for C#, and information about the ecosystem and production support is limited.

Who It’s For and Access from China

RSQL is suitable for new or controllable internal C# systems, small to midsize applications that rely only on basic T-SQL, and teams that want to preserve the option of falling back to SQL Server. It is not suitable for systems that already make heavy use of advanced SQL Server features.

The source text does not provide information about access from China, so its availability is unknown. Since it is free and open source, there is no commercial payment information. If you need a more mature ecosystem, consider SQL Server, PostgreSQL, MySQL/MariaDB, SQLite, or Firebird.