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Using dblink in PostgreSQL
The dblink module allows you to create a bridge between PostgreSQL and other databases, including Oracle. To use dblink, follow these steps:
1. Installation
Since PostgreSQL 9.1, dblink is a built-in extension. Install it using the following command:
CREATE EXTENSION dblink;
If you want to install it in a specific schema, use this syntax:
CREATE EXTENSION dblink SCHEMA my_schema;
2. Connection Parameters
To connect to a remote database, you need to provide the following connection parameters:
3. Connecting with Oracle Syntax
To access tables in the remote database using Oracle syntax, use the following format:
SELECT * FROM table@remote_dblink;
Where remote_dblink is the name of the dblink connection you created using the connection parameters above.
4. Error Handling
If you encounter the following error:
HINT: No function matches the given name and argument types.
You might need to cast the data types explicitly. For example:
SELECT logindate::timestamp FROM dblink(...)
5. Remote Database Configuration
On the remote database server, ensure that it is configured to allow incoming connections from the host you are trying to connect from. You might need to grant privileges to the user you are connecting as.
6. Checking Connection
To check if the connection is working properly, use the following command:
SELECT dblink_connect_u('connection_string');
If the connection is successful, the function will return a non-null value.
Additional Notes:
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