Allows ClickHouse to connect to external databases via [ODBC](https://en.wikipedia.org/wiki/Open_Database_Connectivity).
To implement ODBC connection, ClickHouse uses the separate program `clickhouse-odbc-bridge`. ClickHouse starts this program automatically when it is required. The ODBC bridge program is installed by the same package with the ClickHouse server.
This engine supports the [Nullable](../../data_types/nullable.md) data type.
-`external_database` — Database in an external DBMS.
-`external_table` — A name of the table in `external_database`.
## Usage Example
Some examples of how to use external dictionaries through ODBC you can find in the [ODBC](../../query_language/dicts/external_dicts_dict_sources.md#dicts-external_dicts_dict_sources-odbc) section of external dictionaries configuration.