Extract week from date

Hi again,

I need to extract date grouped by week from an statistics table.

I was trying something like this:

SELECT total_duration, EXTRACT( week from date statistics_date )
FROM statistics_daily
GROUP BY EXTRACT( week from date statistics_date ), total_duration;

But it doesn't works... Neither:

SELECT total_duration, statistics_date
FROM statistics_daily
GROUP BY EXTRACT( day from statistics_date ), total_duration,
statistics_date;

How can it be done?

Note: statistics_date is a DATE data type column.

Regards.

--
Dani Castaños Sánchez
dcastanos(at)androme(dot)es