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@ -21,13 +21,8 @@ Užduotis
-------- --------
Susikurkime PostgreSQL lentelę su viso pasaulio oro uostais (bent tais, kurie Susikurkime PostgreSQL lentelę su viso pasaulio oro uostais (bent tais, kurie
turi [IATA kodą][1]) ir pažaiskime su duomenimis. Turėdami visus pasaulio oro turi [IATA kodą][1]) ir pažaiskime su duomenimis. Toliau tekste -- atsakymas į keletą
uostus galime sugalvoti daug klausimų, bet man šiuo metu įdomu: su kelionėmis ir oro uostais susijusių klausimų.
- 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]?
Duomenų bazės sukūrimas Duomenų bazės sukūrimas
----------------------- -----------------------
@ -75,10 +70,8 @@ Užklausos
``` ```
SELECT SELECT
a.country AS a_country, a.country AS a_country,
a.name AS a_name,
a.iata AS a_iata, a.iata AS a_iata,
b.country AS b_country, b.country AS b_country,
b.name AS b_name,
b.iata AS b_iata, b.iata AS b_iata,
to_char(st_distance (a.geom, b.geom, TRUE) / 1000, '99999.99') AS distance_km to_char(st_distance (a.geom, b.geom, TRUE) / 1000, '99999.99') AS distance_km
FROM FROM
@ -91,28 +84,27 @@ WHERE
ORDER BY ORDER BY
distance_km DESC distance_km DESC
LIMIT 10; LIMIT 10;
a_country | a_name | a_iata | b_country | b_name | b_iata | distance_km
------------------+-------------------------------------+--------+-------------------------+------------------------------------+--------+------------- a_country | a_iata | b_country | 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 China | ZQZ | Argentina | OES | 20002.42
Indonesia | Radin Inten II (Branti) Airport | TKG | Colombia | Mariquita Airport | MQU | 20000.53 Saudi Arabia | KMX | French Polynesia | PUK | 20000.78
French Polynesia | Napuka Island Airport | NAU | Ethiopia | Axum Airport | AXU | 20000.47 Indonesia | TKG | Colombia | MQU | 20000.53
Nicaragua | Corn Island | RNI | Cocos (Keeling) Islands | Cocos (Keeling) Islands Airport | CCK | 20000.20 French Polynesia | NAU | Ethiopia | AXU | 20000.47
China | Jinggangshan Airport | JGS | Argentina | Teniente Benjamin Matienzo Airport | TUC | 19999.93 Nicaragua | RNI | Cocos (Keeling) Islands | CCK | 20000.20
Malaysia | Long Lellang Airport | LGL | Brazil | Tefé Airport | TFF | 19998.43 China | JGS | Argentina | TUC | 19999.93
New Zealand | Hamilton International Airport | HLZ | Spain | Córdoba Airport | ODB | 19998.36 Malaysia | LGL | Brazil | TFF | 19998.43
Indonesia | Sultan Mahmud Badaruddin II Airport | PLM | Colombia | Benito Salas Airport | NVA | 19998.19 New Zealand | HLZ | Spain | ODB | 19998.36
Malaysia | Sultan Ismail Petra Airport | KBR | Peru | Chachapoyas Airport | CHH | 19998.13 Indonesia | PLM | Colombia | NVA | 19998.19
Malaysia | KBR | Peru | CHH | 19998.13
``` ```
**Kurie oro uostai yra arčiausiai vienas kito?** **Kurie oro uostai yra arčiausiai vienas kito?**
``` ```
SELECT SELECT
a.country AS a_country, a.country AS a_country,
a.name AS a_name,
a.iata AS a_iata, a.iata AS a_iata,
b.country AS b_country, b.country AS b_country,
b.name AS b_name,
b.iata AS b_iata, b.iata AS b_iata,
to_char(st_distance (a.geom, b.geom, TRUE) / 1000, '99999.99') AS distance_km to_char(st_distance (a.geom, b.geom, TRUE) / 1000, '99999.99') AS distance_km
FROM FROM
@ -123,27 +115,101 @@ WHERE
AND b.iata != '\N' AND b.iata != '\N'
AND a.gid > b.gid AND a.gid > b.gid
ORDER BY ORDER BY
distance_km ASC a.geom <-> b.geom ASC
LIMIT 10; LIMIT 10;
a_country | a_name | a_iata | b_country | b_name | b_iata | distance_km
------------------+---------------------------------------+--------+------------------+-----------------------------------------------------+--------+------------- a_country | a_iata | b_country | 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 Australia | JHQ | Australia | WSY | 0.14
Papua New Guinea | Kagi Airport | KGW | Papua New Guinea | Efogi Airport | EFG | 2.24 Papua New Guinea | NDN | Papua New Guinea | KGW | 1.83
Rwanda | Gisenyi Airport | GYI | Congo (Kinshasa) | Goma International Airport | GOM | 2.38 Papua New Guinea | KGW | Papua New Guinea | EFG | 2.24
United Kingdom | Westray Airport | WRY | United Kingdom | Papa Westray Airport | PPW | 2.83 Rwanda | GYI | Congo (Kinshasa) | GOM | 2.38
Papua New Guinea | Nadunumu Airport | NDN | Papua New Guinea | Efogi Airport | EFG | 2.92 United Kingdom | WRY | United Kingdom | PPW | 2.83
Papua New Guinea | Bodinumu Airport | BNM | Papua New Guinea | Kagi Airport | KGW | 3.13 Papua New Guinea | NDN | Papua New Guinea | EFG | 2.92
Virgin Islands | Charlotte Amalie Harbor Seaplane Base | SPB | Virgin Islands | Cyril E. King Airport | STT | 3.46 Papua New Guinea | BNM | Papua New Guinea | KGW | 3.13
United States | Brown Field Municipal Airport | SDM | Mexico | General Abelardo L. Rodríguez International Airport | TIJ | 3.59 Virgin Islands | SPB | Virgin Islands | STT | 3.46
French Guiana | Saint-Laurent-du-Maroni Airport | LDX | Suriname | Albina Airport | ABN | 3.71 United States | SDM | Mexico | TIJ | 3.59
French Guiana | LDX | Suriname | ABN | 3.71
``` ```
**Kokį atstumą skristume aplink žemę, jei iš Vilniaus skristume ta pačia platuma?** Dėl pirmų 4 oro uostų įrodymų neradau, kad jie greta, bet WRY ir PPW
**Kiek kartų reikia nuskristi United Economy klase aplink žemę Vilniaus tikrai [netoli][4].
platumoje, kad uždirbtume [nemokamus pusryčius][2]?**
**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;
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
```
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 [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 [2]: https://www.united.com/ual/en/us/fly/mileageplus/premier/full-premier-benefits-chart.html
[3]: https://openflights.org/data.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