In a multi-server MySQL environment, it may be necessary to join tables across databases residing on different physical servers. This article explores how to achieve this inter-server join using Python's MySQLDB module.
MySQL provides the FEDERATED storage engine, which allows tables to be defined across multiple databases on different servers. This approach involves creating a "federated" database that contains a reference to a table on a remote server. To establish the federation, use the following syntax:
CREATE TABLE federated_table ( ... ) ENGINE=FEDERATED DEFAULT CONNECTION='connection_string'
Replace "connection_string" with the connection parameters for the remote server.
As an alternative to the FEDERATED storage engine, you can use an intermediate database as a data integration layer. Establish a connection to the intermediate database and create views that reference tables in the remote databases. Then, perform joins on the views within the intermediate database.
Using Python's MySQLDB module for both approaches, the following code demonstrates the inter-server join:
import MySQLdb # Establish connections to the remote databases conn_server1 = MySQLdb.connect(...) conn_server2 = MySQLdb.connect(...) # Create cursors cursor1 = conn_server1.cursor() cursor2 = conn_server2.cursor() # Intermediate database approach # Create a view in the intermediate database cursor1.execute(...) # Perform the join on the view cursor1.execute(...) # FEDERATED approach # Create a federated table cursor1.execute(...) # Perform the join on the federated table cursor1.execute(...)
Inter-server joins in MySQL can be achieved using either the FEDERATED storage engine or an intermediate database as a data integration layer. Both methods allow for seamless data integration and manipulation across multiple databases on different servers.
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