1.0 KiB
MySQL
The MySQL engine allows you to perform SELECT queries on data that is stored on a remote MySQL server.
The engine takes 5 - 7 parameters: the server address (host and port); the name of the database; the name of the table; the user's name; the user's password. Example:
MySQL('host:port', 'database', 'table', 'user', 'password'[, replace_query, 'on_duplicate_clause' ]);
At this time, simple WHERE clauses such as =, !=, >, >=, <, <=
are executed on the MySQL server.
The rest of the conditions and the LIMIT sampling constraint are executed in ClickHouse only after the query to MySQL finishes.
If replace_query
is specified to 1, then INSERT INTO
query to this table would be transformed to REPLACE INTO
.
If on_duplicate_clause
is specified, eg update impression = values(impression) + impression
, it would add on_duplicate_clause
to the end of the MySQL insert sql.
If both replace_query
and on_duplicate_clause
are specified, only the on_duplicate_clause
will work.