sql - How to select the lowest and highest value joined in one row postgres -


i have data in similar format this

+--------+------------+-------+ | type   | variety    | price | +--------+------------+-------+ | apple  | gala       |  2.79 |  | apple  | fuji       |  0.24 |  | apple  | limbertwig |  2.87 |  | orange | valencia   |  3.59 |  | orange | navel      |  9.36 |  | pear   | bradford   |  6.05 |  | pear   | bartlett   |  2.14 |  | cherry | bing       |  2.55 |  | cherry | chelan     |  6.33 |  +--------+------------+-------+

and want row per type highest price , lowest price so, variety should taken form row highest price

+--------+------------+-------+-------+ | type   | variety    | min   | max   | +--------+------------+-------+-------+ | apple  | limbertwig |  0.24 |  2.87 | | orange | navel      |  9.36 |  3.59 | | pear   | bradford   |  6.05 |  2.14 | | cherry | chelan     |  6.33 |  2.55 | +--------+------------+-------+-------+

what best way achieve using postgres?

i found site: how select first/least/max row per group in sql, it's not quite need.

find fruits lowest price:

select distinct on (type) type, variety, price fruits order 1, 3;   type   | variety  | price  --------+----------+-------  apple  | fuji     |  0.24  cherry | bing     |  2.55  orange | valencia |  3.59  pear   | bartlett |  2.14 (4 rows)

find fruits highest price:

select distinct on (type) type, variety, price fruits order 1, 3 desc;   type   |  variety   | price  --------+------------+-------  apple  | limbertwig |  2.87  cherry | chelan     |  6.33  orange | navel      |  9.36  pear   | bradford   |  6.05 (4 rows)

combine 2 queries:

select      f1.type,      f1.variety min_variety, f1.price min_price,      f2.variety max_variety, f2.price max_price (     select distinct on (type) type, variety, price     fruits     order 1, 3) f1 join (     select distinct on (type) type, variety, price     fruits     order 1, 3 desc) f2 on f1.type = f2.type   type   | min_variety | min_price | max_variety | max_price  --------+-------------+-----------+-------------+-----------  apple  | fuji        |      0.24 | limbertwig  |      2.87  cherry | bing        |      2.55 | chelan      |      6.33  orange | valencia    |      3.59 | navel       |      9.36  pear   | bartlett    |      2.14 | bradford    |      6.05 (4 rows)

alternative cannot use postgres great features:

select      f1.type,      f1.variety min_variety, f1.price min_price,      f2.variety max_variety, f2.price max_price (     select f.type, f.variety, f.price     (         select type, min(price) minprice         fruits group type         ) x      join fruits f on f.type = x.type , f.price = x.minprice     ) f1 join (     select f.type, f.variety, f.price     (         select type, max(price) maxprice         fruits group type         ) x      join fruits f on f.type = x.type , f.price = x.maxprice     ) f2 on f1.type = f2.type order 1;

Comments

Post a Comment

Popular posts from this blog

html - Outlook 2010 Anchor (url/address/link) -

i'm trying link specific pdf page msoutlook'10 or msword'10, #page=... anchor particularly useful , works fine elsewhere. unfortunately when click [ctr-k] in outlook or winword, links re-formatted assuming unc path. pdf file located on shared drive. using "file:" prefix links open pdf in adobe reader (outside of browser), , "http:" open inside browser. issue seem need open in browser "file:" prefix in order anchor work. know anchors work inside browser. outlook uses windows/explorer default program (based on file extension) seems open in adobe reader neglecting anchor. is aware of solution, link specific page or bookmark of shared-pdf ms outlook and/or winword link? common references: mailermailer.com/...anchor-tags-html-emails campaignmonitor.com/...anchor-links-in-email-newsletters/ stackoverflow.com/...anchor-in-pdf-document
Read more

javascript - Why does running this loop 9 times take 100x longer than running it 8 times? -

consider code: test = function() { } t = new test(); (var = 0; < 8; i++) { result = t instanceof test; } if change number of iterations 8 9 , loop take 100 times longer complete in latest version of firefox (41.0.1). tested on 2 different pcs , magic limit 8. here jsperf test used: http://jsperf.com/instanceof-8-times-vs-9-times does have idea why might happen? seems specific instanceof . not happen if else object, example check property. note: filed bugzilla bug this. jan de mooij mozilla team has posted details in bugzilla thread . here's simplistic interpretation of highly technical answers: in i < 8 case, firefox smart enough hoist result = t instanceof test; statement out of loop (according tests, doesn't seem omit altogether). in i < 9 case, apparently doesn't optimization . why? reason not clear, related fact 9 iterations threshold above function considered "hot" enough run through jit compiler. i < 8 cas...
Read more

Getting gateway time-out Rails app with Nginx + Puma running on Digital Ocean -

following this guide setup app on digital ocean droplet, not working. site not loading , it's throwing: "gateway time-out". the puma server works, since ps aux | grep puma prints: root 15878 0.0 0.4 376832 2168 ? sl 12:50 0:00 puma 2.13.4 (unix:///var/www/myapp/shared/tmp/sockets/myapp-puma.sock) [20150930164940] root 15881 0.0 0.7 903676 3692 ? sl 12:50 0:06 puma: cluster worker 0: 15878 [20150930164940] root 24654 0.0 0.1 11748 916 pts/2 s+ 18:00 0:00 grep --color=auto puma my nginx config: user root; worker_processes 1; events { worker_connections 1024; } http { upstream puma { server unix:///var/www/myapp/shared/tmp/sockets/myapp-puma.sock; } server { listen 80; server_name myapp.com; root /var/www/myapp/current/public; access_log /var/www/myapp/current/log/access.log; error_log /...
Read more