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[数据库]关于SQL的相关笔记【长期更新,只发一帖】

场景【1】多表联查时,主表与关联表同时与同一张(第三张表)有关联,类似三角恋关系- -


涉及表:

  • HOUSE:记录了房屋信息
  • ROOMS:记录了房间信息
  • HOUSE_STATUS:记录了状态信息的中文字段

房屋信息HOUSE表中有一个关于记录房屋状态的字段,status_id,与HOUSE_STATUS的主键表关联,而房间信息ROOMS表中,也有一个关于记录房屋状态的字段,也是status_id,当HOUSE与ROOMS建立关联查询时,两张表又分别需要与HOUSE_STATUS这张表建立关联查询。则出现了标题说的三角恋关系,查询方式只需要利用别名查询即可:

SELECT HOUSE.ID, HOUSE.NAME, HOUSE.FLOOR, HOUSE.EXPECT_PRICE, HOUSE.AREA_NUMBER, HOUSE.HAVE_KITCKEN, HOUSE.HAVE_BALCONY, PROVINCE.provinceName, CITY.cityName, AREA.areaName, COMMUNITY.ID       community_ID, COMMUNITY.NAME      community_Name, HOUSE_LAYOUT.NAME    layout_Name, DECORATION_TYPE.NAME   decorationType_Name, HOUSE_STATUS.STATUS_NAME houseStatus_Name, PAYMENT.PAYMENT_NAME   payment_Name, RENT_MODE.ID       rentMode_ID, RENT_MODE.NAME      rentMode_Name, ROOMS.ID, ROOMS.ROOM_NO, ROOMS.HOUSE_STATUS_ID, ROOMS.AREA_NUMBER, ROOMS.EXPECT_PRICE, ROOMS.HAVE_WASHROOM, ROOMS.HAVE_KITCKEN, ROOMS.HOUSE_STATUS_ID, ROOMS.HAVE_DESK, ROOMS.HAVE_AIRCONDITIONING, ROOMS.HAVE_WARDROBE, ROOMS.HAVE_WATERHEATER, ROOMS.HAVE_WLAN, rooms_Status.ID     rooms_StatusID, rooms_Status.STATUS_NAME rooms_StatusNameFROM HOUSE JOIN PROVINCE ON HOUSE.PROVINCE_ID = PROVINCE.provinceID JOIN CITY ON HOUSE.CITY_ID = CITY.cityID JOIN AREA ON HOUSE.AREA_ID = AREA.areaID JOIN COMMUNITY ON HOUSE.COMMUNITY_ID = COMMUNITY.ID JOIN HOUSE_LAYOUT ON HOUSE.LAYOUT_ID = HOUSE_LAYOUT.ID JOIN DECORATION_TYPE ON HOUSE.DECORATION_TYPE_ID = DECORATION_TYPE.ID JOIN HOUSE_STATUS ON HOUSE.HOUSE_STATUS_ID = HOUSE_STATUS.ID JOIN PAYMENT ON HOUSE.EXPECT_PAYMENT_ID = PAYMENT.ID JOIN HOUSE_RENT_MODE ON HOUSE.ID = HOUSE_RENT_MODE.HOUSE_ID JOIN RENT_MODE ON HOUSE_RENT_MODE.RENT_MODE_ID = RENT_MODE.ID JOIN ROOMS ON HOUSE.ID = ROOMS.HOUSE_ID JOIN HOUSE_STATUS rooms_Status ON ROOMS.HOUSE_STATUS_ID = rooms_Status.IDWHERE HOUSE.ID = 1