How Can I Achieve Cross-Database Joins in MySQL Like Oracle's Database Links?

MySQL Equivalent to Oracle Database Link

Oracle's database link feature enables queries across multiple physical databases. However, does MySQL offer a comparable solution to facilitate cross-database joins?

Workarounds for MySQL

While MySQL lacks a direct equivalent to Oracle's database link, several workarounds can address the need for inter-database joins:

1. Fully-Qualified Table Names: Use the dbname.tablename syntax when accessing tables outside the current database scope. This approach requires the connected user to have appropriate read permissions for the external table.
2. Replication: If the external database resides on a different MySQL server, replication can create a read-only copy of the remote table. Note that replication only works between separate MySQL instances.
3. FEDERATED Storage Engine: Import the external table virtually into the current database using the FEDERATED storage engine. This option does not require additional user permissions but may have performance limitations.
4. View Creation: Create a view based on a SELECT statement to access the external table without specifying the fully-qualified table name, providing a convenient alternative to method 1. This approach is limited to tables on the same MySQL instance.

Suitable Workaround Selection

The most suitable workaround depends on specific requirements. For example, method 4 offers convenience but is limited to the same instance. Method 1 provides direct access but requires explicit table name specification. Method 2 offers a read-only solution between separate MySQL instances. Method 3 is less efficient and has certain limitations.

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