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

    【Schema】
    【DB_ID】 card_games
【Schema】
# Table: set_translations
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(language:TEXT, Examples: [Chinese Simplified, Chinese Traditional, French]),
(setCode:TEXT, Examples: [10E, 4ED, 5DN]),
(translation:TEXT, Examples: [核心系列第十版])
]
# Table: legalities
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(format:TEXT, Examples: [commander, duel, legacy]),
(status:TEXT, Examples: [Legal, Banned, Restricted]),
(uuid:TEXT, Examples: [5f8287b1-5bb6-5f4c-ad17-316a40d5bb0c])
]
# Table: cards
[
(id:INTEGER, Primary Key, Examples: [41138, 1349, 23810]),
(artist:TEXT, Examples: [Pete Venters, Volkan Baǵa, Justin Sweet]),
(asciiName:TEXT, Examples: [El-Hajjaj, Junun Efreet, Dandan]),
(availability:TEXT, Examples: [mtgo,paper, paper, arena]),
(borderColor:TEXT, Examples: [black, white, borderless]),
(cardKingdomFoilId:TEXT, Examples: [123094, 123095, 123096]),
(cardKingdomId:TEXT, Examples: [122719, 122720, 122725]),
(colorIdentity:TEXT, Examples: [W, B, U]),
(colorIndicator:TEXT, Examples: [U, G, R]),
(colors:TEXT, Examples: [W, B, U]),
(convertedManaCost:REAL, Examples: [7.0, 5.0, 4.0]),
(duelDeck:TEXT, Examples: [a, b]),
(edhrecRank:INTEGER, Examples: [15650, 12702, 11081]),
(faceConvertedManaCost:REAL, Examples: [4.0, 5.0, 6.0]),
(faceName:TEXT, Examples: [Dusk, Dawn, Commit]),
(flavorName:TEXT, Examples: [Godzilla, King of the Monsters]),
(flavorText:TEXT),
(frameEffects:TEXT, Examples: [legendary, nyxtouched, miracle]),
(frameVersion:TEXT, Examples: [2003, 1993, 2015]),
(hand:TEXT, Examples: [1, 0, -2]),
(hasAlternativeDeckLimit:INTEGER, Examples: [0, 1]),
(hasContentWarning:INTEGER, Examples: [0, 1]),
(hasFoil:INTEGER, Examples: [0, 1]),
(hasNonFoil:INTEGER, Examples: [1, 0]),
(isAlternative:INTEGER, Examples: [0, 1]),
(isFullArt:INTEGER, Examples: [0, 1]),
(isOnlineOnly:INTEGER, Examples: [0, 1]),
(isOversized:INTEGER, Examples: [0, 1]),
(isPromo:INTEGER, Examples: [0, 1]),
(isReprint:INTEGER, Examples: [1, 0]),
(isReserved:INTEGER, Examples: [0, 1]),
(isStarter:INTEGER, Examples: [0, 1]),
(isStorySpotlight:INTEGER, Examples: [0, 1]),
(isTextless:INTEGER, Examples: [0, 1]),
(isTimeshifted:INTEGER, Examples: [0, 1]),
(keywords:TEXT, Examples: [First strike, Flying, First strike,Flash]),
(layout:TEXT, Examples: [normal, aftermath, split]),
(leadershipSkills:TEXT),
(life:TEXT, Examples: [-5, -1, 2]),
(loyalty:TEXT, Examples: [6, 3, 4]),
(manaCost:TEXT, Examples: [{5}{W}{W}, {4}{W}, {3}{W}]),
(mcmId:TEXT, Examples: [16165, 16166, 16171]),
(mcmMetaId:TEXT, Examples: [156, 176, 368]),
(mtgArenaId:TEXT, Examples: [74983, 74986, 74987]),
(mtgjsonV4Id:TEXT, Examples: [ad41be73-582f-58ed-abd4-a88c1f616ac3]),
(mtgoFoilId:TEXT, Examples: [27501, 26993, 27473]),
(mtgoId:TEXT, Examples: [27500, 26992, 27472]),
(multiverseId:TEXT, Examples: [130550, 129465, 129470]),
(name:TEXT, Examples: [Ancestor's Chosen, Angel of Mercy, Aven Cloudchaser]),
(number:TEXT, Examples: [1, 2, 7]),
(originalReleaseDate:TEXT, Examples: [2012/12/1, 2006/12/1, 2007/12/1]),
(originalText:TEXT),
(originalType:TEXT, Examples: [Creature - Human Cleric]),
(otherFaceIds:TEXT, Examples: [87f0062a-8321-5c16-960e-a12ce1df5839]),
(power:TEXT, Examples: [4, 3, 2]),
(printings:TEXT),
(promoTypes:TEXT, Examples: [boxtopper,boosterfun, boosterfun, release,buyabox]),
(purchaseUrls:TEXT),
(rarity:TEXT, Examples: [uncommon, common, rare]),
(scryfallId:TEXT, Examples: [7a5cd03c-4227-4551-aa4b-7d119f0468b5]),
(scryfallIllustrationId:TEXT, Examples: [be2f7173-c8b7-4172-a388-9b2c6b3c16e5]),
(scryfallOracleId:TEXT, Examples: [fc2ccab7-cab1-4463-b73d-898070136d74]),
(setCode:TEXT, Examples: [10E, 2ED, 2XM]),
(side:TEXT, Examples: [a, b, c]),
(subtypes:TEXT, Examples: [Human,Cleric, Angel, Bird,Soldier]),
(supertypes:TEXT, Examples: [Legendary, Basic, Legendary,Snow]),
(tcgplayerProductId:TEXT, Examples: [15032, 15033, 15045]),
(text:TEXT),
(toughness:TEXT, Examples: [4, 3, 2]),
(type:TEXT, Examples: [Creature — Human Cleric]),
(types:TEXT, Examples: [Creature, Instant, Enchantment]),
(uuid:TEXT, Examples: [00010d56-fe38-5e35-8aed-518019aa36a5]),
(variations:TEXT, Examples: [b7c19924-b4bf-56fc-aa73-f586e940bd42]),
(watermark:TEXT, Examples: [set (HOU), set (LGN), set (ONS)])
]
# Table: sets
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(baseSetSize:INTEGER, Examples: [383, 302, 332]),
(block:TEXT, Examples: [Core Set, Mirrodin, Kaladesh]),
(booster:TEXT),
(code:TEXT, Examples: [10E, 2ED, 2XM]),
(isFoilOnly:INTEGER, Examples: [0, 1]),
(isForeignOnly:INTEGER, Examples: [0, 1]),
(isNonFoilOnly:INTEGER, Examples: [0, 1]),
(isOnlineOnly:INTEGER, Examples: [0, 1]),
(isPartialPreview:INTEGER, Examples: [0, 1]),
(keyruneCode:TEXT, Examples: [10E, 2ED, 2XM]),
(mcmId:INTEGER, Examples: [74, 3204, 10]),
(mcmIdExtras:INTEGER, Examples: [3209, 3459, 2587]),
(mcmName:TEXT, Examples: [Tenth Edition, Double Masters, Fourth Edition]),
(mtgoCode:TEXT, Examples: [10E, 2XM, 5DN]),
(name:TEXT, Examples: [Tenth Edition, Unlimited Edition, Double Masters]),
(parentCode:TEXT, Examples: [JMP, MH1, ZNR]),
(releaseDate:DATE, Examples: [2007-07-13]),
(tcgplayerGroupId:INTEGER, Examples: [1, 115, 2655]),
(totalSetSize:INTEGER, Examples: [508, 302, 384]),
(type:TEXT, Examples: [core, masters, expansion])
]
# Table: rulings
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(date:DATE, Examples: [2007-07-15]),
(text:TEXT),
(uuid:TEXT, Examples: [6d268c95-c176-5766-9a46-c14f739aba1c])
]
# Table: foreign_data
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(flavorText:TEXT),
(language:TEXT, Examples: [German, Spanish, French]),
(multiverseid:INTEGER, Examples: [148411, 150317, 149934]),
(name:TEXT, Examples: [Ausgewählter der Ahnfrau]),
(text:TEXT),
(type:TEXT, Examples: [Kreatur — Mensch, Kleriker]),
(uuid:TEXT, Examples: [5f8287b1-5bb6-5f4c-ad17-316a40d5bb0c])
]
【Foreign keys】
set_translations.setCode=sets.code
legalities.uuid=cards.uuid
rulings.uuid=cards.uuid
foreign_data.uuid=cards.uuid

    【Question】
    Give the code of sets have expansion type of 'expansion'? code of sets refers to setCode

    【Evidence】
    code of sets refers to setCode

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

SQL: SELECT T2.setCode FROM sets AS T1 INNER JOIN set_translations AS T2 ON T2.setCode = T1.code WHERE T1.type = 'expansion' GROUP BY T2.setCode