MySQL wire

ClickHouse implements the MySQL wire protocol so existing MySQL tooling can connect without changes. Default port: 9004. Implementation: src/Server/MySQLHandler.cpp and src/Server/MySQLHandlerFactory.cpp, with parser/types support under src/Core/MySQL/ and src/Parsers/MySQL/.

mysql -h localhost -P 9004 -u user -p

What works

• SELECT, INSERT, CREATE TABLE, ALTER, DROP.
• ClickHouse-flavoured SQL (the dialect is ClickHouse, not MySQL — but most MySQL queries that don't use server-side functions land fine).
• Parameterised statements (prepared statements).
• Authentication: mysql_native_password, caching_sha2_password (default in MySQL 8+).
• TLS via the configured server certificate.
• Streaming result sets.

What doesn't

• MySQL-specific server functions (@@version, INFORMATION_SCHEMA flavour quirks) are mapped where reasonable but not exhaustively.
• Stored procedures, triggers, MySQL replication.
• Some MySQL-only built-in functions.

The handler intentionally errs on the side of compatibility. When in doubt about a feature, it returns a clear error rather than silently misbehaving.

Mapping

src/Core/MySQL/MySQLReplication.cpp, MySQLPackets.cpp, MySQLClient.cpp, and the data-type mapping under src/DataTypes/DataTypeNumberBase.cpp translate ClickHouse types to MySQL column types:

• Int* / UInt* → MySQL int types of matching width.
• Float32 / Float64 → FLOAT / DOUBLE.
• String → VARCHAR / TEXT.
• Date, DateTime → MySQL DATE, DATETIME.
• Decimal → DECIMAL.
• UUID, IPv4, IPv6, Enum* → string-ified.

Use cases

• BI tools that speak MySQL (Tableau, Looker, Metabase) can query ClickHouse via JDBC's MySQL driver.
• One-off mysql shell access.
• Migration windows where you need to expose ClickHouse to MySQL-only consumers.

For new clients you control, prefer the native TCP or HTTP interface — they have less impedance mismatch.

MySQL-as-a-source

The reverse direction is also supported: MySQL table engine and mysql(...) table function let ClickHouse pull from a MySQL server. The replication-replica path uses src/Databases/MySQL/ and MaterializedMySQL engine to mirror an upstream MySQL database. See Other engines.

Related pages

• Server protocols
• Postgres wire
• Other engines — MySQL engine, MaterializedMySQL.