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MSSQL vs MySQL: Which Database Should You Choose?

August 20, 2026 by Chat2DB Team

Microsoft SQL Server and MySQL both store relational data reliably and both will handle whatever your application throws at them. The decision between them is rarely about raw capability — it is about licensing, the ecosystem you already run, and how much your team's SQL habits are worth.

This comparison covers where they genuinely differ, with the syntax details that matter when you port code between them.

Licensing and cost

This is usually the deciding factor, so it goes first.

MySQL is open source under the GPL. The Community Edition is free for any use, including commercial deployment. Oracle sells Enterprise Edition with additional backup, monitoring and security features, but a very large number of production systems run Community and never pay anything. MariaDB, a fork with a compatible protocol, is another free path.

SQL Server is commercial. The free tiers are real but limited: Express caps a database at 10 GB and uses at most 1 GB of RAM and the lesser of 4 cores or one socket; Developer Edition is fully featured but licensed only for non-production use. Production means Standard or Enterprise, licensed per core, and the cost is significant — Enterprise runs into five figures per core pair, before Software Assurance.

The counterargument is that licence cost is not total cost. If your organisation already has an enterprise agreement, has SQL Server DBAs, and runs on Windows Server and Active Directory, SQL Server may be cheaper in practice than retraining a team on MySQL.

Platform and ecosystem

MySQL runs on Linux, Windows, macOS and BSD, and is the default database in most Linux hosting environments. Every managed cloud offering supports it — RDS, Aurora, Cloud SQL, Azure Database for MySQL — and the LAMP-era tooling remains vast.

SQL Server has run on Linux since 2017, and that port is a genuine one rather than a compatibility layer, including in containers. But the surrounding ecosystem is still Microsoft-shaped: SQL Server Integration Services, Reporting Services, Analysis Services, Power BI integration and Active Directory authentication are where much of the value sits, and those are strongest on Windows.

If you are building on .NET, Azure and Windows, SQL Server fits without friction. If you are on Linux, Kubernetes and open-source infrastructure, MySQL fits without friction. Fighting that grain is possible but rarely rewarding.

SQL dialect differences

Both are ANSI SQL at the core and diverge everywhere else. These are the differences that break a port:

Identifier quoting:

-- SQL Server
SELECT [order], [user] FROM [dbo].[orders];
 
-- MySQL
SELECT `order`, `user` FROM orders;

MySQL accepts double quotes only with ANSI_QUOTES enabled; SQL Server accepts them with QUOTED_IDENTIFIER ON, which is the default.

Limiting rows:

-- SQL Server
SELECT TOP 10 * FROM orders ORDER BY created_at DESC;
 
SELECT * FROM orders
ORDER BY created_at DESC
OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY;
 
-- MySQL
SELECT * FROM orders ORDER BY created_at DESC LIMIT 10;
SELECT * FROM orders ORDER BY created_at DESC LIMIT 10 OFFSET 20;

Auto-increment keys:

-- SQL Server
CREATE TABLE users (
  id    INT IDENTITY(1,1) PRIMARY KEY,
  email NVARCHAR(255) NOT NULL UNIQUE
);
 
-- MySQL
CREATE TABLE users (
  id    INT AUTO_INCREMENT PRIMARY KEY,
  email VARCHAR(255) NOT NULL UNIQUE
);

String concatenation and NULL handling:

-- SQL Server
SELECT first_name + ' ' + last_name AS full_name FROM users;
SELECT CONCAT(first_name, ' ', last_name) FROM users;  -- also works
SELECT ISNULL(nickname, 'n/a') FROM users;
 
-- MySQL
SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;
SELECT IFNULL(nickname, 'n/a') FROM users;

MySQL's || is a logical OR by default, not concatenation. COALESCE works in both and is the portable choice.

Dates:

-- SQL Server
SELECT GETDATE(), SYSUTCDATETIME();
SELECT DATEADD(day, -7, GETDATE());
SELECT DATEDIFF(day, created_at, GETDATE()) FROM orders;
 
-- MySQL
SELECT NOW(), UTC_TIMESTAMP();
SELECT DATE_SUB(NOW(), INTERVAL 7 DAY);
SELECT DATEDIFF(NOW(), created_at) FROM orders;

Note that DATEDIFF takes different arguments in each and returns results in different units — a silent behaviour change rather than a syntax error, which makes it one of the more dangerous differences.

Procedural code: T-SQL and MySQL's stored program language are entirely different. Variables use DECLARE @name in T-SQL and DECLARE name in MySQL, error handling uses TRY...CATCH versus DECLARE HANDLER, and temporary tables (#temp versus CREATE TEMPORARY TABLE) differ. Stored procedures never port automatically.

Working across both dialects at once is where a client that understands each one helps — Chat2DB (opens in a new tab) connects to SQL Server and MySQL side by side and can translate a query from one dialect to the other, which shortens the tedious part of a migration.

Concurrency and isolation

The default behaviour differs in a way that surprises people moving in either direction.

MySQL with InnoDB defaults to REPEATABLE READ and uses multi-version concurrency control, so readers never block writers and writers never block readers. A SELECT sees a consistent snapshot without taking locks.

SQL Server defaults to READ COMMITTED implemented with shared locks, so a read can block behind a write. This is why WITH (NOLOCK) became folklore in SQL Server codebases — it is a workaround for lock contention, and one that permits dirty reads. The better fix is to enable snapshot isolation:

ALTER DATABASE appdb SET READ_COMMITTED_SNAPSHOT ON;

That gives SQL Server MVCC-style behaviour for read-committed transactions, at the cost of extra tempdb usage. New SQL Server deployments should generally turn it on; Azure SQL Database has it on by default.

Indexes and storage

SQL Server organises tables around a clustered index you choose, plus non-clustered indexes that store a key lookup. It also offers filtered indexes, included columns, and columnstore indexes for analytical workloads — the last of which is a real advantage for reporting against large tables:

CREATE NONCLUSTERED INDEX ix_orders_status
  ON orders (status)
  INCLUDE (total_amount, created_at)
  WHERE status <> 'archived';
 
CREATE CLUSTERED COLUMNSTORE INDEX cci_facts ON fact_sales;

MySQL's InnoDB always clusters on the primary key, which is not optional — secondary indexes store the primary key value, so a wide primary key makes every index larger. That makes primary key choice more consequential in MySQL than in SQL Server. MySQL 8 added functional indexes and descending indexes, but has no equivalent of columnstore in the community edition.

Practical consequence: keep MySQL primary keys narrow (a BIGINT or a UUIDv7 stored as BINARY(16), not a long natural key), and take advantage of SQL Server's INCLUDE columns to build covering indexes without widening the key.

JSON

Both support JSON, differently.

MySQL has a native JSON column type with binary storage, plus generated columns you can index:

CREATE TABLE events (
  id      BIGINT AUTO_INCREMENT PRIMARY KEY,
  payload JSON NOT NULL,
  user_id BIGINT AS (payload->>'$.user_id') STORED,
  INDEX (user_id)
);
 
SELECT payload->>'$.event_type' FROM events WHERE user_id = 42;

SQL Server stores JSON as NVARCHAR and provides functions over it. Indexing means a computed column:

CREATE TABLE events (
  id      BIGINT IDENTITY PRIMARY KEY,
  payload NVARCHAR(MAX) NOT NULL
    CONSTRAINT ck_payload_json CHECK (ISJSON(payload) = 1),
  user_id AS CAST(JSON_VALUE(payload, '$.user_id') AS BIGINT) PERSISTED,
  INDEX ix_events_user (user_id)
);
 
SELECT JSON_VALUE(payload, '$.event_type') FROM events WHERE user_id = 42;

MySQL's native type validates and stores JSON more compactly. SQL Server 2025 introduced a native json type, but on earlier versions in wide production use the NVARCHAR approach is what you will meet.

Replication and high availability

MySQL offers asynchronous and semi-synchronous replication, GTID-based failover, and Group Replication with InnoDB Cluster for automatic failover. It is flexible and free, but you assemble it — orchestration usually means ProxySQL, Orchestrator or a managed service.

SQL Server offers Always On Availability Groups: synchronous or asynchronous replicas, automatic failover, readable secondaries, and a listener that redirects clients transparently. It is more integrated and more polished, and it requires Enterprise Edition for more than a basic single-database group.

Choosing

Choose SQL Server if you build on .NET and Azure, need Always On availability groups or columnstore analytics, rely on SSIS or SSRS, authenticate through Active Directory, or already have the licences and the DBA expertise.

Choose MySQL if licence cost matters, you deploy on Linux or containers, your stack is PHP, Python, Node.js or Java on open-source infrastructure, or you want the widest choice of managed hosting and the option to move between providers.

Consider neither if your workload is heavily analytical (look at ClickHouse or a warehouse) or you need advanced types, extensions and window-function depth (PostgreSQL sits between the two on licensing and ahead of both on SQL features, which is why it has taken so much greenfield work).

For most new projects that are not already anchored to Microsoft's stack, MySQL's licensing and portability win. For teams inside that stack, SQL Server's integration is worth more than the cost of a licence — and that is a legitimate answer, not a compromise.