Oracle9i SQL Reference Release 2 (9.2) Part Number A96540-01 |
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SQL Queries and Subqueries, 11 of 11
Oracle's distributed database management system architecture lets you access data in remote databases using Oracle Net and an Oracle server. You can identify a remote table, view, or materialized view by appending @dblink to the end of its name. The dblink must be a complete or partial name for a database link to the database containing the remote table, view, or materialized view.
See Also:
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Restrictions on Distributed Queries
Distributed queries are currently subject to the restriction that all tables locked by a FOR
UPDATE
clause and all tables with LONG
columns selected by the query must be located on the same database. For example, the following statement will raise an error:
SELECT employees_ny.* FROM employees_ny@ny, departments WHERE employees_ny.department_id = departments.department_id AND departments.department_name = 'ACCOUNTING' FOR UPDATE OF employees_ny.salary;
The following statement fails because it selects long_column
, a LONG
value, from the employees_review
table on the ny
database and locks the employees
table on the local database:
SELECT employees.employee_id, review.long_column, employees.salary FROM employees, employees_review@ny review WHERE employees.employee_id = employees_review.employee_id FOR UPDATE OF employees.salary;
In addition, Oracle currently does not support distributed queries that select user-defined types or object REF
s on remote tables.
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