Re: [SQL] nested select within a DISCTINCT block
On 14 sep 2006, at 23.58, Daryl Richter wrote: create table booking(booking_id int, customer_id int, product_package_id int, details text); create table cancellation(cancellation_id int , booking_id int, charge decimal); insert into booking values( 1, 1, 1, 'Cxl Booking 1' ); insert into booking values( 2, 2, 1, 'Cxl Booking 2' ); insert into booking values( 3, 2, 1, 'Ok Booking 3' ); insert into booking values( 4, 3, 2, 'Cxl Booking 4' ); insert into cancellation values( 1, 1, 1.00 ); insert into cancellation values( 2, 2, 1.00 ); insert into cancellation values( 3, 4, 1.00 ); select distinct product_package_id, ( select count(booking_id) from booking b2 where b2.product_package_id = b1.product_package_id and not exists ( select 1 from cancellation c where c.booking_id = b2.booking_id ) ) as uncancelled_bookings from booking b1 order by product_package_id; product_package_id uncancelled_bookings - --- 1 1 2 0 Given the above, you could also phrase it a little more natural, as follows: SELECT product_package_id, COUNT(b.booking_id)-COUNT(c.booking_id) AS un_cancelled_bookings FROM booking b LEFT JOIN cancellation c USING(booking_id) GROUP BY product_package_id ORDER BY product_package_id; I don't know about the amount and distribution of data in this case, but I think this will also give you a slightly better plan in most cases. Sincerely, Niklas Johansson ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [SQL] nested select within a DISCTINCT block
Thanks alot!!! Daryl Richter-2 wrote: > > On 9/14/06 1:13 PM, "zqzuk" <[EMAIL PROTECTED]> wrote: > >> >> 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 ! >> > > create table booking(booking_id int, customer_id int, product_package_id > int, details text); > > create table cancellation(cancellation_id int , booking_id int, charge > decimal); > > insert into booking values( 1, 1, 1, 'Cxl Booking 1' ); > insert into booking values( 2, 2, 1, 'Cxl Booking 2' ); > insert into booking values( 3, 2, 1, 'Ok Booking 3' ); > insert into booking values( 4, 3, 2, 'Cxl Booking 4' ); > > insert into cancellation values( 1, 1, 1.00 ); > insert into cancellation values( 2, 2, 1.00 ); > insert into cancellation values( 3, 4, 1.00 ); > > > select distinct product_package_id, >( select count(booking_id) > from booking b2 > where > b2.product_package_id = b1.product_package_id > and not exists ( select 1 from cancellation c where c.booking_id = > b2.booking_id ) ) as uncancelled_bookings > from booking b1 > order by product_package_id; > > product_package_id uncancelled_bookings > - --- > 1 1 > 2 0 > > 2 record(s) selected [Fetch MetaData: 2/ms] [Fetch Data: 0/ms] > > [Executed: 9/14/06 5:56:07 PM EDT ] [Execution: 86/ms] > > > -- > Daryl > http://itsallsemantics.com > > "I¹m afraid of the easy stuff its always harder than it seems" > -- Bill Hampton, 2006 > > > > > > ---(end of broadcast)--- > TIP 3: Have you checked our extensive FAQ? > >http://www.postgresql.org/docs/faq > > -- View this message in context: http://www.nabble.com/nested-select-within-a-DISCTINCT-block-tf2272951.html#a6315840 Sent from the PostgreSQL - sql forum at Nabble.com. ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [SQL] nested select within a DISCTINCT block
On 9/14/06 1:13 PM, "zqzuk" <[EMAIL PROTECTED]> wrote: > > 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 ! > create table booking(booking_id int, customer_id int, product_package_id int, details text); create table cancellation(cancellation_id int , booking_id int, charge decimal); insert into booking values( 1, 1, 1, 'Cxl Booking 1' ); insert into booking values( 2, 2, 1, 'Cxl Booking 2' ); insert into booking values( 3, 2, 1, 'Ok Booking 3' ); insert into booking values( 4, 3, 2, 'Cxl Booking 4' ); insert into cancellation values( 1, 1, 1.00 ); insert into cancellation values( 2, 2, 1.00 ); insert into cancellation values( 3, 4, 1.00 ); select distinct product_package_id, ( select count(booking_id) from booking b2 where b2.product_package_id = b1.product_package_id and not exists ( select 1 from cancellation c where c.booking_id = b2.booking_id ) ) as uncancelled_bookings from booking b1 order by product_package_id; product_package_id uncancelled_bookings - --- 1 1 2 0 2 record(s) selected [Fetch MetaData: 2/ms] [Fetch Data: 0/ms] [Executed: 9/14/06 5:56:07 PM EDT ] [Execution: 86/ms] -- Daryl http://itsallsemantics.com "I¹m afraid of the easy stuff its always harder than it seems" -- Bill Hampton, 2006 ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
