SQL query error

Hello, 

I am trying to create this query to calculate opportunity age:

SELECT opportunities.id opportunity_id, opportunities.name opportunity_name, datediff(date(now()), date(opportunities.date_created)) opportunity_age_in_days, date(opportunities.date_created) created_at, date(opportunities.date_modified) updated_at, date(opportunities.date_closed) as closed_at
FROM opportunities

however I keep getting this error: 

Not Found

The requested URL was not found on this server.

Could you please let me know why?