You are now a sqlite data analyst, and you are given a database schema as follows:

    【Schema】
    【DB_ID】 mondial_geo
【Schema】
# Table: lake
[
(Name:TEXT, Primary Key, Examples: [Ammersee, Arresoe, Atlin Lake]),
(Area:REAL, Examples: [46.6, 40.2, 798.0]),
(Depth:REAL, Examples: [81.1, 5.6, 283.0]),
(Altitude:REAL, Examples: [533.0, 668.0, 104.0]),
(Type:TEXT, Examples: [artificial, salt, caldera]),
(River:TEXT, Examples: [Ammer, Yukon River, Sanaga]),
(Longitude:REAL, Examples: [11.6, 12.1, -133.75]),
(Latitude:REAL, Examples: [48.0, 56.0, 59.5])
]
# Table: geo_island
[
(Island:TEXT, Primary Key, Examples: [Aland, Alicudi, Ambon]),
(Country:TEXT, Primary Key, Examples: [Alan, Lipa, Molu]),
(Province:TEXT, Primary Key, Examples: [101, 102, 10244])
]
# Table: sea
[
(Name:TEXT, Primary Key, Examples: [Andaman Sea, Arabian Sea, Arctic Ocean]),
(Depth:REAL, Examples: [3113.0, 5203.0, 5608.0])
]
# Table: island
[
(Name:TEXT, Primary Key, Examples: [Aland, Alicudi, Ambon]),
(Islands:TEXT, Examples: [Aland Islands, Lipari Islands, Moluccan Islands]),
(Area:REAL, Examples: [650.0, 5.2, 775.0]),
(Height:REAL, Examples: [675.0, 1225.0, 32.0]),
(Type:TEXT, Examples: [volcanic, lime, coral]),
(Longitude:REAL, Examples: [20.0, 14.4, 128.2]),
(Latitude:REAL, Examples: [60.1, 38.6, -3.7])
]
# Table: city
[
(Name:TEXT, Primary Key, Examples: [Aachen, Aalborg, Aarau]),
(Country:TEXT, Examples: [D, DK, CH]),
(Province:TEXT, Primary Key, Examples: [Nordrhein Westfalen, Denmark, AG]),
(Population:INTEGER, Examples: [247113, 113865, 194345]),
(Longitude:REAL, Examples: [10.0, 10.1, -4.0]),
(Latitude:REAL, Examples: [57.0, 56.1, 5.3])
]
# Table: ethnicGroup
[
(Country:TEXT, Primary Key, Examples: [GE, EAU, DJI]),
(Name:TEXT, Primary Key, Examples: [Abkhaz, Acholi, Afar]),
(Percentage:REAL, Examples: [1.8, 4.0, 35.0])
]
# Table: country
[
(Name:TEXT, Examples: [Afghanistan, Albania, Algeria]),
(Code:TEXT, Primary Key, Examples: [A, AFG, AG]),
(Capital:TEXT, Examples: [Vienna, Kabul, Saint Johns]),
(Province:TEXT, Examples: [Vienna, Afghanistan, Antigua and Barbuda]),
(Area:REAL, Examples: [83850.0, 647500.0, 442.0]),
(Population:INTEGER, Examples: [8023244, 22664136, 65647])
]
# Table: locatedOn
[
(City:TEXT, Primary Key, Examples: [Aberdeen, Aberystwyth, Adamstown]),
(Province:TEXT, Primary Key, Examples: [Province, Grampian, Ceredigion]),
(Country:TEXT, Primary Key, Examples: [Coun, GB, PITC]),
(Island:TEXT, Primary Key, Examples: [Island, Great Britain, Pitcairn])
]
# Table: river
[
(Name:TEXT, Primary Key, Examples: [Aare, Adda, Akagera]),
(River:TEXT, Examples: [Rhein, Po, Ohio River]),
(Lake:TEXT, Examples: [Brienzersee, Lago di Como, Lake Victoria]),
(Sea:TEXT, Examples: [Atlantic Ocean, Sea of Okhotsk, Mediterranean Sea]),
(Length:REAL, Examples: [288.0, 313.0, 275.0]),
(SourceLongitude:REAL, Examples: [8.2, 10.3, 29.3]),
(SourceLatitude:REAL, Examples: [46.55, -2.5, 41.9]),
(Mountains:TEXT, Examples: [Alps]),
(SourceAltitude:REAL, Examples: [2310.0, 2235.0, 2700.0]),
(EstuaryLongitude:REAL, Examples: [8.22, 9.88, 33.0]),
(EstuaryLatitude:REAL, Examples: [47.61, 45.13, -1.0])
]
# Table: geo_mountain
[
(Mountain:TEXT, Primary Key, Examples: [Mountain, Gran Sasso, Tirich Mir]),
(Country:TEXT, Primary Key, Examples: [Coun, I, AFG]),
(Province:TEXT, Primary Key, Examples: [Abruzzo, Afghanistan, Agri])
]
# Table: located
[
(City:TEXT, Examples: [City, Shkoder, Durres]),
(Province:TEXT, Examples: [Province]),
(Country:TEXT, Examples: [Coun, AL, GR]),
(River:TEXT, Examples: [River, Donau, Save]),
(Lake:TEXT, Examples: [Lake, Lake Skutari, Bodensee]),
(Sea:TEXT, Examples: [Sea, Mediterranean Sea, Atlantic Ocean])
]
# Table: mountainOnIsland
[
(Mountain:TEXT, Primary Key, Examples: [Andringitra, Asahi-Dake, Barbeau Peak]),
(Island:TEXT, Primary Key, Examples: [Island, Madagaskar, Hokkaido])
]
# Table: isMember
[
(Country:TEXT, Primary Key, Examples: [A, AFG, AG]),
(Organization:TEXT, Primary Key, Examples: [AG, ANC, AfDB]),
(Type:TEXT, Examples: [Type, nonregional member, observer])
]
# Table: borders
[
(Country1:TEXT, Primary Key, Examples: [A, AFG, AL]),
(Country2:TEXT, Primary Key, Examples: [CH, CZ, D]),
(Length:REAL, Examples: [164.0, 362.0, 784.0])
]
# Table: religion
[
(Country:TEXT, Primary Key, Examples: [BERM, AUS, AXA]),
(Name:TEXT, Primary Key, Examples: [African Methodist Episcopal]),
(Percentage:REAL, Examples: [11.0, 26.1, 29.0])
]
# Table: mountain
[
(Name:TEXT, Primary Key),
(Mountains:TEXT),
(Height:REAL),
(Type:TEXT),
(Longitude:REAL),
(Latitude:REAL)
]
# Table: population
[
(Country:TEXT, Primary Key, Examples: [A, AFG, AG]),
(Population_Growth:REAL, Examples: [0.41, 4.78, 0.76]),
(Infant_Mortality:REAL, Examples: [6.2, 149.7, 17.2])
]
# Table: geo_source
[
(River:TEXT, Primary Key, Examples: [River, White Nile, Amudarja]),
(Country:TEXT, Primary Key, Examples: [Coun, SUD, AFG]),
(Province:TEXT, Primary Key, Examples: [Aali an Nil, Afghanistan, Agri])
]
# Table: organization
[
(Abbreviation:TEXT, Primary Key, Examples: [ABEDA, ACC, ACCT]),
(Name:TEXT, Examples: [ASEAN-Mekong Basin Development Group]),
(City:TEXT, Examples: [City, Khartoum, Paris]),
(Country:TEXT, Examples: [Coun, SUD, F]),
(Province:TEXT, Examples: [Province, al Khartum, Ile de France]),
(Established:DATE)
]
# Table: desert
[
(Name:TEXT, Primary Key, Examples: [Arabian Desert, Atacama, Azaouad]),
(Area:REAL, Examples: [50000.0, 181300.0, 80000.0]),
(Longitude:REAL, Examples: [26.0, -69.25, 0.0]),
(Latitude:REAL, Examples: [33.0, -24.5, 20.0])
]
# Table: politics
[
(Country:TEXT, Primary Key, Examples: [A, AFG, AG]),
(Independence:DATE),
(Dependent:TEXT, Examples: [Depe, USA, NL]),
(Government:TEXT, Examples: [Government])
]
# Table: mergesWith
[
(Sea1:TEXT, Primary Key, Examples: [Andaman Sea, Arabian Sea, Arctic Ocean]),
(Sea2:TEXT, Primary Key, Examples: [Sea2, Gulf of Bengal, Indian Ocean])
]
# Table: encompasses
[
(Country:TEXT, Primary Key, Examples: [A, AFG, AG]),
(Continent:TEXT, Primary Key, Examples: [Europe, Asia, America]),
(Percentage:REAL, Examples: [100.0, 90.0, 10.0])
]
# Table: continent
[
(Name:TEXT, Primary Key, Examples: [Africa, America, Asia]),
(Area:REAL, Examples: [30254700.0, 39872000.0, 45095300.0])
]
# Table: province
[
(Name:TEXT, Primary Key, Examples: [AG, AI, AR]),
(Country:TEXT, Primary Key, Examples: [CH, SUD, GB]),
(Population:INTEGER, Examples: [1599605, 110700, 1263000]),
(Area:REAL, Examples: [238792.0, 1130.0, 10794.0]),
(Capital:TEXT, Examples: [Malakal, Colwyn Bay, LAquila]),
(CapProv:TEXT, Examples: [Aali an Nil, Aberconwy and Colwyn, Abruzzo])
]
# Table: geo_river
[
(River:TEXT, Primary Key, Examples: [River]),
(Country:TEXT, Primary Key, Examples: [Coun, SUD, IRQ]),
(Province:TEXT, Primary Key, Examples: [AG, Aali an Nil, Ad Tamim])
]
# Table: language
[
(Country:TEXT, Primary Key, Examples: [AFG, NAM, MK]),
(Name:TEXT, Primary Key, Examples: [Afghan Persian, Afrikaans, Albanian]),
(Percentage:REAL, Examples: [50.0, 60.0, 21.0])
]
# Table: economy
[
(Country:TEXT, Primary Key, Examples: [A, AFG, AG]),
(GDP:REAL, Examples: [152000.0, 12800.0, 425.0]),
(Agriculture:REAL, Examples: [2.0, 65.0, 3.5]),
(Service:REAL, Examples: [34.0, 15.0, 19.3]),
(Industry:REAL, Examples: [64.0, 20.0, 77.2]),
(Inflation:REAL, Examples: [2.3, 3.5, 16.0])
]
# Table: islandIn
[
(Island:TEXT, Examples: [Island, Svalbard, Greenland]),
(Sea:TEXT, Examples: [Sea, Norwegian Sea, Barents Sea]),
(Lake:TEXT, Examples: [Lake, Ozero Baikal, Lake Toba]),
(River:TEXT, Examples: [River])
]
# Table: target
[
(Country:TEXT, Primary Key, Examples: [A, AFG, AL]),
(Target:TEXT, Examples: [Target, Christian, non-Christian])
]
# Table: geo_desert
[
(Desert:TEXT, Primary Key, Examples: [Desert, Rub Al Chali, Dascht-e-Margoh]),
(Country:TEXT, Primary Key, Examples: [Coun, UAE, AFG]),
(Province:TEXT, Primary Key, Examples: [Abu Dhabi, Afghanistan, Ahal])
]
# Table: geo_estuary
[
(River:TEXT, Primary Key, Examples: [River]),
(Country:TEXT, Primary Key, Examples: [Coun, SUD, AFG]),
(Province:TEXT, Primary Key, Examples: [AG, Aali an Nil, Afghanistan])
]
# Table: geo_sea
[
(Sea:TEXT, Primary Key, Examples: [Sea, Mediterranean Sea, Persian Gulf]),
(Country:TEXT, Primary Key, Examples: [Coun, I, UAE]),
(Province:TEXT, Primary Key, Examples: [Abruzzo, Abu Dhabi, Adana])
]
# Table: geo_lake
[
(Lake:TEXT, Primary Key, Examples: [Lake, Barrage de Mbakaou, Lake Nicaragua]),
(Country:TEXT, Primary Key, Examples: [Coun, CAM, CR]),
(Province:TEXT, Primary Key, Examples: [Adamaoua, Alajuela, Albania])
]
【Foreign keys】
geo_island.Province=province.Name
geo_island.Country=province.Country
geo_island.Country=country.Code
geo_island.Island=island.Name
city.Province=province.Name
city.Country=province.Country
city.Country=country.Code
ethnicGroup.Country=country.Code
locatedOn.Province=province.Name
locatedOn.Country=province.Country
locatedOn.City=city.Name
locatedOn.Province=city.Province
locatedOn.Island=island.Name
locatedOn.Country=country.Code
river.Lake=lake.Name
geo_mountain.Province=province.Name
geo_mountain.Country=province.Country
geo_mountain.Country=country.Code
geo_mountain.Mountain=mountain.Name
located.Province=province.Name
located.Country=province.Country
located.City=city.Name
located.Province=city.Province
located.Sea=sea.Name
located.Lake=lake.Name
located.River=river.Name
located.Country=country.Code
mountainOnIsland.Island=island.Name
mountainOnIsland.Mountain=mountain.Name
isMember.Organization=organization.Abbreviation
isMember.Country=country.Code
borders.Country2=country.Code
borders.Country1=country.Code
religion.Country=country.Code
population.Country=country.Code
geo_source.Province=province.Name
geo_source.Country=province.Country
geo_source.Country=country.Code
geo_source.River=river.Name
organization.Province=province.Name
organization.Country=province.Country
organization.City=city.Name
organization.Province=city.Province
organization.Country=country.Code
politics.Dependent=country.Code
politics.Country=country.Code
mergesWith.Sea2=sea.Name
mergesWith.Sea1=sea.Name
encompasses.Continent=continent.Name
encompasses.Country=country.Code
province.Country=country.Code
geo_river.Province=province.Name
geo_river.Country=province.Country
geo_river.Country=country.Code
geo_river.River=river.Name
language.Country=country.Code
economy.Country=country.Code
islandIn.River=river.Name
islandIn.Lake=lake.Name
islandIn.Sea=sea.Name
islandIn.Island=island.Name
target.Country=country.Code
geo_desert.Province=province.Name
geo_desert.Country=province.Country
geo_desert.Country=country.Code
geo_desert.Desert=desert.Name
geo_estuary.Province=province.Name
geo_estuary.Country=province.Country
geo_estuary.Country=country.Code
geo_estuary.River=river.Name
geo_sea.Province=province.Name
geo_sea.Country=province.Country
geo_sea.Country=country.Code
geo_sea.Sea=sea.Name
geo_lake.Province=province.Name
geo_lake.Country=province.Country
geo_lake.Country=country.Code
geo_lake.Lake=lake.Name

    【Question】
    When did 'Bulgaria' gain independence?

    【Evidence】
    

    Please read and understand the database schema carefully, and generate an executable SQL based on the user's question and evidence. 

SQL: SELECT T2.Independence FROM country AS T1 INNER JOIN politics AS T2 ON T1.Code = T2.Country WHERE T1.Name = 'Bulgaria'