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133 lines
4.0 KiB
Markdown
133 lines
4.0 KiB
Markdown
---
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machine_translated: true
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machine_translated_rev: 72537a2d527c63c07aa5d2361a8829f3895cf2bd
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toc_priority: 35
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toc_title: ODBC
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---
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# ODBC {#table-engine-odbc}
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允许ClickHouse通过[ODBC](https://en.wikipedia.org/wiki/Open_Database_Connectivity)方式连接到外部数据库.
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为了安全地实现ODBC连接，ClickHouse使用了一个独立程序 `clickhouse-odbc-bridge`. 如果ODBC驱动程序是直接从 `clickhouse-server`中加载的，那么驱动问题可能会导致ClickHouse服务崩溃。 当有需要时，ClickHouse会自动启动 `clickhouse-odbc-bridge`。 ODBC桥梁程序与`clickhouse-server`来自相同的安装包.
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该引擎支持 [可为空](../../../sql-reference/data-types/nullable.md) 的数据类型。
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## 创建表 {#creating-a-table}
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``` sql
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CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
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(
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name1 [type1],
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name2 [type2],
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...
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)
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ENGINE = ODBC(connection_settings, external_database, external_table)
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```
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详情请见 [CREATE TABLE](../../../sql-reference/statements/create.md#create-table-query) 查询。
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表结构可以与源表结构不同:
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- 列名应与源表中的列名相同，但您可以按任何顺序使用其中的一些列。
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- 列类型可能与源表中的列类型不同。 ClickHouse尝试将数值[映射](../../../sql-reference/functions/type-conversion-functions.md#type_conversion_function-cast) 到ClickHouse的数据类型。
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**引擎参数**
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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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## 用法示例 {#usage-example}
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**通过ODBC从本地安装的MySQL中检索数据**
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本示例针对Ubuntu Linux18.04和MySQL服务器5.7进行检查。
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请确保安装了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`clickhouse`的身份启动 . 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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然后在`/etc/odbc.ini`中配置连接 .
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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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您可以从安装的unixodbc中使用 `isql` 实用程序来检查连接情况。
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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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ClickHouse中的表，从MySQL表中检索数据:
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``` sql
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CREATE TABLE odbc_t
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(
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`int_id` Int32,
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`float_nullable` Nullable(Float32)
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)
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ENGINE = ODBC('DSN=mysqlconn', 'test', 'test')
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```
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``` sql
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SELECT * FROM odbc_t
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```
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``` text
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┌─int_id─┬─float_nullable─┐
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│ 1 │ ᴺᵁᴸᴸ │
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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表函数](../../../sql-reference/table-functions/odbc.md)
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[原始文章](https://clickhouse.tech/docs/en/operations/table_engines/odbc/) <!--hide-->
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