ClickHouse/docs/zh/engines/table_engines/integrations/jdbc.md

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---
machine_translated: true
machine_translated_rev: b111334d6614a02564cf32f379679e9ff970d9b1
toc_priority: 34
toc_title: JDBC
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---
# JDBC {#table-engine-jdbc}
允许ClickHouse通过以下方式连接到外部数据库 [JDBC](https://en.wikipedia.org/wiki/Java_Database_Connectivity).
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要实现JDBC连接ClickHouse使用单独的程序 [ツ暗ェツ氾环催ツ団ツ法ツ人](https://github.com/alex-krash/clickhouse-jdbc-bridge) 这应该作为守护进程运行。
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该引擎支持 [可为空](../../../sql_reference/data_types/nullable.md) 数据类型。
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## 创建表 {#creating-a-table}
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``` sql
CREATE TABLE [IF NOT EXISTS] [db.]table_name
(
columns list...
)
ENGINE = JDBC(dbms_uri, external_database, external_table)
```
**发动机参数**
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- `dbms_uri` — URI of an external DBMS.
格式: `jdbc:<driver_name>://<host_name>:<port>/?user=<username>&password=<password>`.
Mysql的示例: `jdbc:mysql://localhost:3306/?user=root&password=root`.
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- `external_database` — Database in an external DBMS.
- `external_table` — Name of the table in `external_database`.
## 用法示例 {#usage-example}
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通过直接与它的控制台客户端连接在MySQL服务器中创建一个表:
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``` text
mysql> CREATE TABLE `test`.`test` (
-> `int_id` INT NOT NULL AUTO_INCREMENT,
-> `int_nullable` INT NULL DEFAULT NULL,
-> `float` FLOAT NOT NULL,
-> `float_nullable` FLOAT NULL DEFAULT NULL,
-> PRIMARY KEY (`int_id`));
Query OK, 0 rows affected (0,09 sec)
mysql> insert into test (`int_id`, `float`) VALUES (1,2);
Query OK, 1 row affected (0,00 sec)
mysql> select * from test;
+------+----------+-----+----------+
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| int_id | int_nullable | float | float_nullable |
+------+----------+-----+----------+
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| 1 | NULL | 2 | NULL |
+------+----------+-----+----------+
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1 row in set (0,00 sec)
```
在ClickHouse服务器中创建表并从中选择数据:
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``` sql
CREATE TABLE jdbc_table
(
`int_id` Int32,
`int_nullable` Nullable(Int32),
`float` Float32,
`float_nullable` Nullable(Float32)
)
ENGINE JDBC('jdbc:mysql://localhost:3306/?user=root&password=root', 'test', 'test')
```
``` sql
SELECT *
FROM jdbc_table
```
``` text
┌─int_id─┬─int_nullable─┬─float─┬─float_nullable─┐
│ 1 │ ᴺᵁᴸᴸ │ 2 │ ᴺᵁᴸᴸ │
└────────┴──────────────┴───────┴────────────────┘
```
## 另请参阅 {#see-also}
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- [JDBC表函数](../../../sql_reference/table_functions/jdbc.md).
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[原始文章](https://clickhouse.tech/docs/en/operations/table_engines/jdbc/) <!--hide-->