CREATE DATABASE 

Creates a new database.

CREATE DATABASE [IF NOT EXISTS] db_name [ON CLUSTER cluster] [ENGINE = engine(...)]

Clauses 

IF NOT EXISTS 

If the db_name database already exists, then ClickHouse does not create a new database and:

• Doesn’t throw an exception if clause is specified.
• Throws an exception if clause isn’t specified.

ON CLUSTER 

ClickHouse creates the db_name database on all the servers of a specified cluster. More details in a Distributed DDL article.

ENGINE 

MySQL allows you to retrieve data from the remote MySQL server. By default, ClickHouse uses its own database engine. There’s also a lazy engine.