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109 lines
3.5 KiB
Markdown
109 lines
3.5 KiB
Markdown
---
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machine_translated: true
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machine_translated_rev: b111334d6614a02564cf32f379679e9ff970d9b1
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toc_priority: 44
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toc_title: odbc
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---
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# odbc {#table-functions-odbc}
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返回通过连接的表 [ODBC](https://en.wikipedia.org/wiki/Open_Database_Connectivity).
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``` sql
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odbc(connection_settings, external_database, external_table)
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```
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参数:
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- `connection_settings` — Name of the section with connection settings in the `odbc.ini` 文件
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- `external_database` — Name of a database in an external DBMS.
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- `external_table` — Name of a table in the `external_database`.
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为了安全地实现ODBC连接，ClickHouse使用单独的程序 `clickhouse-odbc-bridge`. 如果直接从ODBC驱动程序加载 `clickhouse-server`，驱动程序问题可能会导致ClickHouse服务器崩溃。 ClickHouse自动启动 `clickhouse-odbc-bridge` 当它是必需的。 ODBC桥程序是从相同的软件包作为安装 `clickhouse-server`.
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与字段 `NULL` 外部表中的值将转换为基数据类型的默认值。 例如，如果远程MySQL表字段具有 `INT NULL` 键入它将转换为0（ClickHouse的默认值 `Int32` 数据类型）。
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## 用法示例 {#usage-example}
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**通过ODBC从本地MySQL安装获取数据**
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此示例检查Ubuntu Linux18.04和MySQL服务器5.7。
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确保安装了unixODBC和MySQL连接器。
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默认情况下（如果从软件包安装），ClickHouse以用户身份启动 `clickhouse`. 因此，您需要在MySQL服务器中创建和配置此用户。
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``` bash
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$ sudo mysql
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```
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``` sql
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mysql> CREATE USER 'clickhouse'@'localhost' IDENTIFIED BY 'clickhouse';
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mysql> GRANT ALL PRIVILEGES ON *.* TO 'clickhouse'@'clickhouse' WITH GRANT OPTION;
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```
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然后配置连接 `/etc/odbc.ini`.
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``` bash
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$ cat /etc/odbc.ini
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[mysqlconn]
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DRIVER = /usr/local/lib/libmyodbc5w.so
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SERVER = 127.0.0.1
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PORT = 3306
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DATABASE = test
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USERNAME = clickhouse
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PASSWORD = clickhouse
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```
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您可以使用 `isql` unixodbc安装中的实用程序。
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``` bash
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$ isql -v mysqlconn
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+-------------------------+
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| Connected! |
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| |
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...
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```
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MySQL中的表:
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``` text
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mysql> CREATE TABLE `test`.`test` (
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-> `int_id` INT NOT NULL AUTO_INCREMENT,
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-> `int_nullable` INT NULL DEFAULT NULL,
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-> `float` FLOAT NOT NULL,
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-> `float_nullable` FLOAT NULL DEFAULT NULL,
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-> PRIMARY KEY (`int_id`));
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Query OK, 0 rows affected (0,09 sec)
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mysql> insert into test (`int_id`, `float`) VALUES (1,2);
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Query OK, 1 row affected (0,00 sec)
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mysql> select * from test;
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+------+----------+-----+----------+
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| int_id | int_nullable | float | float_nullable |
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+------+----------+-----+----------+
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| 1 | NULL | 2 | NULL |
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+------+----------+-----+----------+
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1 row in set (0,00 sec)
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```
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从ClickHouse中的MySQL表中检索数据:
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``` sql
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SELECT * FROM odbc('DSN=mysqlconn', 'test', 'test')
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```
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``` text
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┌─int_id─┬─int_nullable─┬─float─┬─float_nullable─┐
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│ 1 │ 0 │ 2 │ 0 │
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└────────┴──────────────┴───────┴────────────────┘
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```
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## 另请参阅 {#see-also}
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- [ODBC外部字典](../../sql_reference/dictionaries/external_dictionaries/external_dicts_dict_sources.md#dicts-external_dicts_dict_sources-odbc)
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- [ODBC表引擎](../../engines/table_engines/integrations/odbc.md).
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[原始文章](https://clickhouse.tech/docs/en/query_language/table_functions/jdbc/) <!--hide-->
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