oracle - Why do SQL code examples demonstrating parallelism comment out the parallel statements? -



oracle - Why do SQL code examples demonstrating parallelism comment out the parallel statements? -

in question oracle: why doesn't utilize parallel execution?

and oracle documentation http://docs.oracle.com/cd/b10500_01/server.920/a96524/c20paral.htm#26156

they're comenting out paralell statement such:

select /*+ parallel(employees 4) parallel(departments 4) use_hash(employees) ordered */ max(salary), avg(salary) employees, departments employees.department_id = departments.department_id grouping employees.department_id;

why doing this?

the oracle 10 documentation clearest on syntax hints:

hint syntax

you can send hints sql statement optimizer enclosing them in comment within statement.

the reason simple. hints enclosed in comment if sql compiler doesn't recognize them, ignored. true different versions of oracle. true code beingness ported other databases. hint can included code still works.

sql oracle parallel-processing

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