commit 55a4bb55c0e49e2e29329dc40f02e9ba1fcc198b (tree)
parent 3b9ded2f57a499d3380e834205bc3cc6f86b2f61
Author: Motiejus Jakštys <desired.mta@gmail.com>
Date: Sat, 26 Oct 2019 18:40:36 +0300
more article
Diffstat:
1 file changed, 105 insertions(+), 39 deletions(-)
diff --git a/MTM/task4-straipsnis/straipsnis.md b/MTM/task4-straipsnis/straipsnis.md
@@ -21,13 +21,8 @@ Užduotis
--------
Susikurkime PostgreSQL lentelę su viso pasaulio oro uostais (bent tais, kurie
-turi [IATA kodą][1]) ir pažaiskime su duomenimis. Turėdami visus pasaulio oro
-uostus galime sugalvoti daug klausimų, bet man šiuo metu įdomu:
-- kokie du oro uostai yra labiausiai nutolę vienas nuo kito?
-- kurie du oro uosta yra arčiausiai vienas kito? O toje pačioje šalyje?
-- kokį atstumą skristume aplink žemę, jei iš Vilniaus skristume ta pačia platuma?
-- kiek kartų reikia nuskristi United Economy klase aplink žemę Vilniaus
- platumoje, kad uždirbtume [nemokamus pusryčius][2]?
+turi [IATA kodą][1]) ir pažaiskime su duomenimis. Toliau tekste -- atsakymas į keletą
+su kelionėmis ir oro uostais susijusių klausimų.
Duomenų bazės sukūrimas
-----------------------
@@ -75,10 +70,8 @@ Užklausos
```
SELECT
a.country AS a_country,
- a.name AS a_name,
a.iata AS a_iata,
b.country AS b_country,
- b.name AS b_name,
b.iata AS b_iata,
to_char(st_distance (a.geom, b.geom, TRUE) / 1000, '99999.99') AS distance_km
FROM
@@ -91,28 +84,27 @@ WHERE
ORDER BY
distance_km DESC
LIMIT 10;
- a_country | a_name | a_iata | b_country | b_name | b_iata | distance_km
-------------------+-------------------------------------+--------+-------------------------+------------------------------------+--------+-------------
- China | Zhangjiakou Ningyuan Airport | ZQZ | Argentina | Antoine de Saint Exupéry Airport | OES | 20002.42
- Saudi Arabia | King Khaled Air Base | KMX | French Polynesia | Pukarua Airport | PUK | 20000.78
- Indonesia | Radin Inten II (Branti) Airport | TKG | Colombia | Mariquita Airport | MQU | 20000.53
- French Polynesia | Napuka Island Airport | NAU | Ethiopia | Axum Airport | AXU | 20000.47
- Nicaragua | Corn Island | RNI | Cocos (Keeling) Islands | Cocos (Keeling) Islands Airport | CCK | 20000.20
- China | Jinggangshan Airport | JGS | Argentina | Teniente Benjamin Matienzo Airport | TUC | 19999.93
- Malaysia | Long Lellang Airport | LGL | Brazil | Tefé Airport | TFF | 19998.43
- New Zealand | Hamilton International Airport | HLZ | Spain | Córdoba Airport | ODB | 19998.36
- Indonesia | Sultan Mahmud Badaruddin II Airport | PLM | Colombia | Benito Salas Airport | NVA | 19998.19
- Malaysia | Sultan Ismail Petra Airport | KBR | Peru | Chachapoyas Airport | CHH | 19998.13
+
+ a_country | a_iata | b_country | b_iata | distance_km
+------------------+--------+-------------------------+--------+-------------
+ China | ZQZ | Argentina | OES | 20002.42
+ Saudi Arabia | KMX | French Polynesia | PUK | 20000.78
+ Indonesia | TKG | Colombia | MQU | 20000.53
+ French Polynesia | NAU | Ethiopia | AXU | 20000.47
+ Nicaragua | RNI | Cocos (Keeling) Islands | CCK | 20000.20
+ China | JGS | Argentina | TUC | 19999.93
+ Malaysia | LGL | Brazil | TFF | 19998.43
+ New Zealand | HLZ | Spain | ODB | 19998.36
+ Indonesia | PLM | Colombia | NVA | 19998.19
+ Malaysia | KBR | Peru | CHH | 19998.13
```
**Kurie oro uostai yra arčiausiai vienas kito?**
```
SELECT
a.country AS a_country,
- a.name AS a_name,
a.iata AS a_iata,
b.country AS b_country,
- b.name AS b_name,
b.iata AS b_iata,
to_char(st_distance (a.geom, b.geom, TRUE) / 1000, '99999.99') AS distance_km
FROM
@@ -123,27 +115,101 @@ WHERE
AND b.iata != '\N'
AND a.gid > b.gid
ORDER BY
- distance_km ASC
+ a.geom <-> b.geom ASC
+LIMIT 10;
+
+ a_country | a_iata | b_country | b_iata | distance_km
+------------------+--------+------------------+--------+-------------
+ Australia | JHQ | Australia | WSY | 0.14
+ Papua New Guinea | NDN | Papua New Guinea | KGW | 1.83
+ Papua New Guinea | KGW | Papua New Guinea | EFG | 2.24
+ Rwanda | GYI | Congo (Kinshasa) | GOM | 2.38
+ United Kingdom | WRY | United Kingdom | PPW | 2.83
+ Papua New Guinea | NDN | Papua New Guinea | EFG | 2.92
+ Papua New Guinea | BNM | Papua New Guinea | KGW | 3.13
+ Virgin Islands | SPB | Virgin Islands | STT | 3.46
+ United States | SDM | Mexico | TIJ | 3.59
+ French Guiana | LDX | Suriname | ABN | 3.71
+```
+
+Dėl pirmų 4 oro uostų įrodymų neradau, kad jie greta, bet WRY ir PPW
+tikrai [netoli][4].
+
+**Aukščiausiai virš jūros lygio esantys oro uostai?**
+
+```
+SELECT
+ iata,
+ name,
+ country,
+ to_char(st_z (geom), '9999') AS altitude_m
+FROM
+ airports
+ORDER BY
+ altitude_m DESC
+LIMIT 10;
+
+ iata | name | country | altitude_m
+------+----------------------------------------+---------+------------
+ DCY | Daocheng Yading Airport | China | 4411
+ BPX | Qamdo Bangda Airport | China | 4334
+ KGT | Kangding Airport | China | 4280
+ NGQ | Ngari Gunsa Airport | China | 4274
+ LPB | El Alto International Airport | Bolivia | 4071
+ POI | Capitan Nicolas Rojas Airport | Bolivia | 3936
+ YUS | Yushu Batang Airport | China | 3906
+ \N | Copacabana Airport | Bolivia | 3838
+ JUL | Inca Manco Capac International Airport | Peru | 3826
+ GMQ | Golog Maqin Airport | China | 3787
+```
+
+**Žemiausiai po jūros lygiu esantys oro uostai?**
+
+```
+SELECT
+ iata,
+ name,
+ country,
+ to_char(st_z (geom), 'FMSG999.00') AS altitude_m
+FROM
+ airports
+WHERE
+ iata != '\N'
+ORDER BY
+ st_z (geom) ASC
LIMIT 10;
- a_country | a_name | a_iata | b_country | b_name | b_iata | distance_km
-------------------+---------------------------------------+--------+------------------+-----------------------------------------------------+--------+-------------
- Australia | Shute Harbour Airport | JHQ | Australia | Whitsunday Island Airport | WSY | 0.14
- Papua New Guinea | Nadunumu Airport | NDN | Papua New Guinea | Kagi Airport | KGW | 1.83
- Papua New Guinea | Kagi Airport | KGW | Papua New Guinea | Efogi Airport | EFG | 2.24
- Rwanda | Gisenyi Airport | GYI | Congo (Kinshasa) | Goma International Airport | GOM | 2.38
- United Kingdom | Westray Airport | WRY | United Kingdom | Papa Westray Airport | PPW | 2.83
- Papua New Guinea | Nadunumu Airport | NDN | Papua New Guinea | Efogi Airport | EFG | 2.92
- Papua New Guinea | Bodinumu Airport | BNM | Papua New Guinea | Kagi Airport | KGW | 3.13
- Virgin Islands | Charlotte Amalie Harbor Seaplane Base | SPB | Virgin Islands | Cyril E. King Airport | STT | 3.46
- United States | Brown Field Municipal Airport | SDM | Mexico | General Abelardo L. Rodríguez International Airport | TIJ | 3.59
- French Guiana | Saint-Laurent-du-Maroni Airport | LDX | Suriname | Albina Airport | ABN | 3.71
+
+ iata | name | country | altitude_m
+------+--------------------------------------+---------------+------------
+ MTZ | Bar Yehuda Airfield | Israel | -385.88
+ EIY | Ein Yahav Airfield | Israel | -49.99
+ TRM | Jacqueline Cochran Regional Airport | United States | -35.05
+ GUW | Atyrau Airport | Kazakhstan | -21.95
+ RZR | Ramsar Airport | Iran | -21.34
+ ASF | Astrakhan Airport | Russia | -19.81
+ NSH | Noshahr Airport | Iran | -18.59
+ IPL | Imperial County Airport | United States | -16.46
+ NJK | El Centro NAF Airport (Vraciu Field) | United States | -12.80
+ RAS | Sardar-e-Jangal Airport | Iran | -12.19
```
-**Kokį atstumą skristume aplink žemę, jei iš Vilniaus skristume ta pačia platuma?**
-**Kiek kartų reikia nuskristi United Economy klase aplink žemę Vilniaus
- platumoje, kad uždirbtume [nemokamus pusryčius][2]?**
+Pabaiga
+-------
+
+Kaip matėme šiame įraše, PostGis suteikia erdvines funkcijas, duomenų tipus ir
+indeksus prie patogios ir pažįstamos PostgreSQL sąsajos.
+
+Užduotys susidomėjusiam skaitytojui:
+* Kodėl artimiausių oro uostų užklausoje naudojome [<->][5], o
+ tolimiausių -- [st_distance][6]?
+* Kokį atstumą skristume aplink žemę, jei iš Vilniaus skristume ta pačia platuma?
+* Kiek kartų reikia nuskristi United Economy klase aplink žemę Vilniaus
+ platumoje, kad uždirbtume [nemokamus pusryčius][2]?
[1]: https://en.wikipedia.org/wiki/International_Air_Transport_Association_code
[2]: https://www.united.com/ual/en/us/fly/mileageplus/premier/full-premier-benefits-chart.html
[3]: https://openflights.org/data.html
+[4]: https://goo.gl/maps/CCkqFvhN9rWfrsxT6
+[5]: https://postgis.net/docs/geometry_distance_knn.html
+[6]: https://postgis.net/docs/ST_Distance.html
