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