如何在 MONGODB 中删除数组中的重复值？
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【中文标题】如何在 MONGODB 中删除数组中的重复值？【英文标题】：How to remove duplicate values inside an array in MONGODB? 【发布时间】：2021-11-24 16:45:46 【问题描述】：个人架构：
[
"_id": "e6f32800-240e-11ec-b291-51abbaa8f015",
"firstName": "A",
"lastName": "Cris",
"phoneNumber": "111-222-3333",
"socialMedia": "FaceBook",
"DOB": "01/01/1990",
"Theater": 1,
"__v": 0
,
"_id": "e7092b90-240f-11ec-8812-d375202a89ac",
"firstName": "A",
"lastName": "Cris",
"phoneNumber": "111-222-3333",
"socialMedia": "FaceBook",
"DOB": "01/01/1990",
"Theater": 2,
"__v": 0
,
"_id": "e8e78880-240f-11ec-8812-d375202a89ac",
"firstName": "A",
"lastName": "Cris",
"phoneNumber": "111-222-3333",
"socialMedia": "Twitter",
"DOB": "01/01/1990",
"Theater": 3,
"__v": 0
,
"_id": "ee20f750-240f-11ec-8812-d375202a89ac",
"firstName": "B",
"lastName": "Hood",
"phoneNumber": "333-444-5555",
"socialMedia": "Friends",
"DOB": "05/05/1993",
"Theater": 1,
"__v": 0
,
"_id": "76d6ad60-2410-11ec-bc7f-8dbab8f2c871",
"firstName": "B",
"lastName": "Hood",
"phoneNumber": "333-444-5555",
"socialMedia": "Radio 900 AM",
"DOB": "05/05/1993",
"Theater": 2,
"__v": 0
,
"_id": "f053b5d0-240f-11ec-8812-d375202a89ac",
"firstName": "B",
"lastName": "Hood",
"phoneNumber": "333-444-5555",
"socialMedia": "Radio 900 AM",
"DOB": "05/05/1993",
"Theater": 3,
"__v": 0
,
"_id": "79946dd0-2410-11ec-bc7f-8dbab8f2c871",
"firstName": "C",
"lastName": "Mohammad",
"phoneNumber": "555-666-7777",
"socialMedia": "Radio 104.2 PM",
"DOB": "10/10/1995",
"Theater": 1,
"__v": 0
,
"_id": "7b4244e0-2410-11ec-bc7f-8dbab8f2c871",
"firstName": "C",
"lastName": "Mohammad",
"phoneNumber": "555-666-7777",
"socialMedia": "News",
"DOB": "10/10/1995",
"Theater": 2,
"__v": 0
,
"_id": "7d097050-2410-11ec-bc7f-8dbab8f2c871",
"firstName": "C",
"lastName": "Mohammad",
"phoneNumber": "555-666-7777",
"socialMedia": "News",
"DOB": "10/10/1995",
"Theater": 3,
"__v": 0
]
电影院架构：
[
"_id": 1,
"TheaterName": "AMC Katy Mill 20",
"location": "Katy, TX",
"__v": 0
,
"_id": 2,
"TheaterName": "AMC First Colony",
"location": "Sugar Land, TX",
"__v": 0
,
"_id": 3,
"TheaterName": "AMC Deer***",
"location": "Humble, TX",
"__v": 0
]
注意：
Individuals 架构中的剧院字段是 _id 的标识符 MovieTheater 架构。
socialMedia 字段是个人了解MovieTheater 的方式
我可以做多少次（计数）个人加入电影院，将所有社交媒体推入一个数组，使用以下方法进行投影：
db.collection.aggregate([
"$group":
"_id":
"firstName": "$firstName",
"lastName": "$lastName",
"phoneNumber": "$phoneNumber",
"DOB": "$DOB"
,
"count":
"$sum": 1
,
"socialMedia":
"$push": "$socialMedia"
,
"$project":
"_id.firstName": 1,
"_id.lastName": 1,
"Count": 1,
"socialMedia": 1
])
输出：
[
"_id":
"firstName": "A",
"lastName": "Cris"
,
"Count": 3,
"socialMedia": [
"FaceBook",
"FaceBook",
"Twitter"
]
,
"_id":
"firstName": "B",
"lastName": "Hood"
,
"Count": 3,
"socialMedia": [
"Radio 900 AM",
"Radio 900 AM",
"Friends"
]
,
"_id":
"firstName": "C",
"lastName": "Mohammad"
,
"Count": 3,
"socialMedia": [
"News",
"News",
"Radio 104.2 PM"
]
]
但我不知道要删除 socialMedia 中的重复值。
我的预期结果如下：
"_id":
"firstName": "A",
"lastName": "Cris"
,
"Count": 3,
"socialMedia": [
"FaceBook",
"Twitter"
]
非常感谢。
【问题讨论】：
【参考方案1】：使用$addToSet 代替$push 代替socialMedia。
$addToSet$addToSet 返回一个包含所有唯一值的数组，这些值是通过将表达式应用于组中的每个文档而产生的。
db.collection.aggregate([
"$group":
"_id":
"firstName": "$firstName",
"lastName": "$lastName",
"phoneNumber": "$phoneNumber",
"DOB": "$DOB"
,
"count":
"$sum": 1
,
"socialMedia":
"$addToSet": "$socialMedia"
,
"$project":
"_id.firstName": 1,
"_id.lastName": 1,
"Count": 1,
"socialMedia": 1
])
Sample Mongo Playground
【讨论】：
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