Hi, here i have a problem with this task...
I have a table "cancellation" which stores cancelled bookings and details of
charges etc
and a table "bookings" which stores details of bookings, for example:
cancellation(cancellation_id, booking_id, charge)
booking(booking_id, customer_id, product_package_id, details)
in the query, i wish to find, how many customers have booked for each
product_package_id. if there were 3 bookings for product_package_id=1, and
all these are cancelled and therefore exist in cancellation, then the query
result shoud display something like
package_id, #of bookings
1 0
here are what i tried
select distinct b.product_package_id,
count (distinct b.customer_id and not exists (select cc from cancellation cc
where cc.booking_id=b.booking_id)) from booking as b
group by b.product_package_id
and it doesnt work. the syntax within the DISTINCT is wrong, unsurprisingly.
i also tried
select distinct b.product_package_id,
count (distinct b.customer_id not in (select cc from cancellation cc where
cc.booking_id=b.booking_id)) from booking as b
group by b.product_package_id
it produced incorrect result. ie, for those canceled bookings are also
counted, producing
package_id, #of bookings
1 3
which supposed to be
package_id, #of bookings
1 0
could anyone give any hints please, many thanks !
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