ClickHouse/tests/integration/test_mysql_database_engine/configs/named_collections.xml

<clickhouse>
    <named_collections>
        <mysql1>
            <user>root</user>
            <password>clickhouse</password>
            <host>mysql57</host>
            <port>3306</port>
            <database>test_database</database>
            <table>test_table</table>
        </mysql1>
        <mysql2>
            <user>postgres</user>
            <password>mysecretpassword</password>
            <host>postgres1</host>
        </mysql2>
        <mysql3>
            <user>root</user>
            <password>clickhouse</password>
            <host>mysql57</host>
            <port>1111</port>
            <database>clickhouse</database>
            <table>test_table</table>
        </mysql3>
    </named_collections>
</clickhouse>