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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteNo open-source database is a transparent drop-in replacement for Microsoft SQL Server. SQL Server uses T-SQL, and code that depends on that dialect, or on SQL Server-specific services, has to be inspected and usually changed. PostgreSQL is the strongest general-purpose starting point. MariaDB and MySQL Community Edition are mature alternatives. CockroachDB and SQLite answer different architectural questions. This guide shows which engine fits which situation and what a migration involves.
The short answer, by situation
| Your situation | Start your evaluation with | Why |
|---|---|---|
| General-purpose server database, permissive open-source licence preferred | PostgreSQL | Open-source object-relational database released under the PostgreSQL License. |
| You want a GPL-licensed server database with documented SQL Server migration guidance | MariaDB Server | GPLv2 general-purpose relational database; its documentation includes a path for migrating from SQL Server, including DDL export for SQL Server sources. |
| Your application ecosystem already assumes MySQL | MySQL Community Edition | Free and open-source; large ecosystem. Expect SQL adaptation if the code leans on SQL Server features. |
| Distributed SQL across nodes or regions is a real requirement | CockroachDB | Supports the PostgreSQL wire protocol and most PostgreSQL syntax; its schema conversion tooling lists SQL Server as a supported source. |
| A single-user or application-local database embedded in the app | SQLite | Embedded engine, not a networked multi-user server. |
| You want to look beyond the mainstream | Firebird, CUBRID | Named in a September 27, 2026 LinuxLinks roundup. Verify them against their official documentation before relying on them. |
This is not a ranking of speed or quality. No common, non-promotional benchmark across these engines was established, so any claim that one is fastest would be unsupported. Test your own workload under identical conditions.
Why there is no drop-in replacement
SQL Server’s dialect is T-SQL. Other engines implement the SQL standard and their own extensions, which differ from T-SQL in syntax, data types, procedural language, and built-in functions. The harder problem is often what sits around the engine. SQL Server deployments commonly include scheduled jobs, integration and reporting services, linked servers, Windows authentication, and application code that embeds T-SQL. None of these moves automatically to a different database.
Two points about compatibility claims are worth keeping straight:
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- MySQL compatibility is not T-SQL compatibility. MariaDB’s own overview says it retains high compatibility with MySQL while the two projects have diverged. That says nothing about running SQL Server code.
- PostgreSQL compatibility is not T-SQL compatibility either. CockroachDB’s support for the PostgreSQL wire protocol and most PostgreSQL syntax helps applications written for PostgreSQL. It does not make SQL Server code run unchanged.
The candidates
PostgreSQL
PostgreSQL is an open-source object-relational database distributed under the PostgreSQL License, according to the project’s official overview and license pages. It is a sensible first candidate for a broad range of relational workloads, particularly when a permissive licence matters to you.
It is not a T-SQL engine. Before you estimate effort, inventory stored procedures, SQL Server-specific data types, scheduled jobs, integrations, and the queries embedded in application code.
MariaDB Server
The MariaDB Foundation describes MariaDB Server as “a general purpose open source relational database management system” and lists GPLv2 as its licence. The notable point for SQL Server shops is that MariaDB’s documentation has an explicit migration-from-SQL-Server path, including a DDL export guide for Microsoft SQL Server sources.
That makes it a credible migration candidate. It does not mean SQL Server code runs unchanged, and a documented schema conversion does not prove that every object in your database can be migrated automatically. Read the current limitations in the MariaDB documentation.
MySQL Community Edition
MySQL Community Edition is a free, open-source option with a large ecosystem. It is worth considering when your applications, frameworks, or hosting already assume MySQL. If your SQL Server code contains a lot of T-SQL, plan for adaptation.
Check Oracle’s current Community Edition licensing and distribution terms directly before you make legal or procurement decisions, especially if you distribute software that embeds or bundles it.
CockroachDB
Cockroach Labs describes CockroachDB as supporting the PostgreSQL wire protocol and the majority of PostgreSQL syntax. Its schema conversion tooling lists SQL Server as a supported source, and its MOLT toolkit and Migration Assistant are described by the vendor as free to use. The same migration page describes paid advisory, embedded, and enterprise migration services.
Treat CockroachDB as a candidate when distributed SQL and its operating model are what you need. These are vendor statements about the destination and its tooling. They are not a guarantee of T-SQL equivalence, full application conversion, or fit for every self-hosted deployment, so validate exact feature support against your schema. If you only need a single well-run server, a conventional engine such as PostgreSQL is a simpler comparison point.
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SQLite
SQLite is an embedded database that lives inside the application. It suits local storage, desktop and mobile apps, and tools that don’t need a database service. It is not a like-for-like replacement for a networked SQL Server instance serving many concurrent users. Establish your deployment and access requirements first. If several applications or users connect over a network, SQLite is probably the wrong category.
Firebird and CUBRID
A LinuxLinks roundup dated September 27, 2026 also names Firebird and CUBRID as alternatives. Firebird is a candidate if you want an embedded or server-capable database, and CUBRID is another relational option. The sources reviewed here don’t document their current feature sets, support status, or licensing in enough detail to recommend either over the engines above. Verify official project documentation before shortlisting them.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to choose: the comparison axes that matter
- Dialect distance and code change. How much T-SQL lives in the database and in application code?
- SQL Server-specific services. Agent jobs, integration and reporting tools, linked servers, and authentication integration all need their own replacements.
- Licensing and distribution. PostgreSQL License (permissive), GPLv2 (MariaDB Server), and Oracle’s Community Edition terms (MySQL) carry different obligations, especially if you ship the database with your product.
- Deployment model. Embedded (SQLite), conventional server (PostgreSQL, MariaDB, MySQL), or distributed (CockroachDB).
- Transaction and workload profile. Measure it on your own data and queries, with the same hardware and settings for every candidate.
- Migration and validation tooling. MariaDB documents SQL Server DDL export; Cockroach Labs documents schema conversion and data migration tools.
- Operations and support. Backup and recovery, monitoring, upgrades, and whether your team can operate the engine or needs paid support.
A migration plan that surfaces problems early
- Inventory everything that touches SQL Server. List T-SQL queries, stored procedures, triggers, SQL Server Agent jobs, data types, indexing choices, authentication, replication, reporting, backup and recovery, and external integrations.
- Classify each item. Decide whether it lives in the engine, in application code, or in Microsoft-specific tooling. Each class needs a different fix.
- Shortlist two engines. Use the axes above. Two candidates are enough to compare real effort without running every option.
- Convert a representative slice. Take a realistic schema and data set, not a toy table. Use the vendor’s documented path, such as MariaDB’s SQL Server DDL export or Cockroach Labs’ schema conversion tooling, and read the current limitations.
- Test behaviour, not just row counts. Run the application’s test suite, compare query results, and validate data types, collation and sorting, null handling, date and time behaviour, and transaction semantics.
- Benchmark your own workload. Use the same hardware, data volume, and concurrency for each candidate.
- Plan cutover and rollback. Rehearse the migration, define how long both systems run, and keep a tested way back until the new system has proven itself.
For complex estates, paid migration help is a legitimate option. Cockroach Labs, for example, describes advisory, embedded, and enterprise migration services for its own platform. Treat that as a vendor offering, not an independent recommendation.
What this comparison does not claim
No independent benchmark, adoption figure, or migration-success or cost-savings statistic was established for these engines, so none appears here. Product versions, licensing terms, service offerings, and tooling limitations change, so confirm them on each project’s official documentation before you commit. Treat the roundup-sourced Firebird and CUBRID mentions as leads, not endorsements.
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