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oracle hint

原创 Linux操作系统 作者:v_fantasy 时间:2009-04-21 19:08:41 0 删除 编辑

DRIVING_SITE Hint

The DRIVING_SITE hint instructs the optimizer to execute the query at a different site than that selected by the database. This hint is useful if you are using distributed query optimization.

For example:

SELECT /*+ DRIVING_SITE(departments) */ * 
  FROM employees, departments@rsite 
  WHERE employees.department_id = departments.department_id;

If this query is executed without the hint, then rows from departments are sent to the local site, and the join is executed there. With the hint, the rows from employees are sent to the remote site, and the query is executed there and the result set is returned to the local site.

当语句在两个库的执行计划不同时,可以通过此hint来选择,保证语句的执行速度。

 

 

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