Retrieving information from two or more nodes - Oracle Distributed Database concepts - Distributed query

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• Nirja Shah   -Posted on 21 Sep 15
  - Distributed query - This statement retrieves information from two or more nodes.
  - For example, the following query accesses data from the local database as well as the remote sales database:
  
  SELECT ename, dname
  FROM scott.emp e, scott.dept@sales.us.americas.acme_auto.com d
  WHERE e.deptno = d.deptno;
  
  - Distributed update - This statement modifies data on two or more nodes.
  - A distributed update is possible using a PL/SQL subprogram unit such as a procedure or trigger that includes two or more remote updates that access data on different nodes.
  - For example, the following PL/SQL program unit updates tables on the local database and the remote sales database:
  
  BEGIN
  UPDATE scott.dept@sales.us.americas.acme_auto.com
  SET loc = 'NEW YORK'
  WHERE deptno = 10;
  UPDATE scott.emp
  SET deptno = 11
  WHERE deptno = 10;
  END;
  COMMIT;
  
  - The database sends statements in the program to the remote nodes, and their execution succeeds or fails as a unit.

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