查询以获取对象数组中只有一个对象的结果对象
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【中文标题】查询以获取对象数组中只有一个对象的结果对象【英文标题】：query to get result object with only one object inside an array of objects 【发布时间】：2018-06-14 01:49:32 【问题描述】：我需要实现一个在线调查 MEAN 堆栈应用程序。我需要从集合中获取一个文档，该集合中只有 inv_users 数组中的对象。我的文档是这样的：
[
"_id": "5a431d73fcaf01ec6274ecbc",
"name": "Patient Satisfaction survey",
"company_id": "5a432162fcaf01ec6274ec89",
"start_datetime": "2017-12-11T06:57:44.650Z",
"end_datetime": "2018-12-11T06:57:44.650Z",
"logo": "",
"header_title": "Patient satisfaction Survey",
"footer_title": "powered by team",
"img_read_code": "",
"mail_responded": true,
"survey_complete": true,
"inv_users": [
"email": "jooshipp@gmail.com",
"ip": "192.168.1.17",
"latitude": 39.02,
"longitude": -119.47,
"survey_completed": false,
"mail_responsed": false,
"mail_viewed": true,
"cmp_user_id": "5a432162fcaf01ec6274ecc0"
,
"email": "jamal@gmail.com",
"ip": "192.168.1.17",
"latitude": 39.02,
"longitude": -119.47,
"survey_completed": false,
"mail_responsed": false,
"mail_viewed": true,
"cmp_user_id": "5a432162fcaf01ec6274ecc8"
],
"answers": [
"answer": "Satisfied",
"date_time": "2017-03-24T12:15:12.000Z",
"ip": "192.168.1.17",
"latitude": 42.05,
"longitude": -119.47,
"global_user_id": "5a431dbafcaf01ec6274ecc0",
"cmp_user_id": ""
],
"questions": [
"question": "Are you satisfied with the appearance",
"ans_type": "Multiple choice",
"options": [
"No",
"Satisfied",
"a little",
"Very Satisfied"
]
],
"is_footer": true,
"is_header": true,
"display_type":
"ui": "single",
"randamization": true,
"pageno": true,
"skip": true,
"randomization": false
,
"category":
"id": "5a4167b5aa77271cb7f228ed",
"name": "Collect Feedback"
]
我的结果应该是这样的：
[
"_id": "5a431d73fcaf01ec6274ecbc",
"name": "Patient Satisfaction survey",
"company_id": "5a432162fcaf01ec6274ec89",
"start_datetime": "2017-12-11T06:57:44.650Z",
"end_datetime": "2018-12-11T06:57:44.650Z",
"logo": "",
"header_title": "Patient satisfaction Survey",
"footer_title": "powered by team",
"img_read_code": "",
"mail_responded": true,
"survey_complete": true,
"inv_users": [
"email": "jooshipp@gmail.com",
"ip": "192.168.1.17",
"latitude": 39.02,
"longitude": -119.47,
"survey_completed": false,
"mail_responsed": false,
"mail_viewed": true,
"cmp_user_id": "5a432162fcaf01ec6274ecc0"
],
"answers": [
"answer": "Satisfied",
"date_time": "2017-03-24T12:15:12.000Z",
"ip": "192.168.1.17",
"latitude": 42.05,
"longitude": -119.47,
"global_user_id": "5a431dbafcaf01ec6274ecc0",
"cmp_user_id": ""
],
"questions": [
"question": "Are you satisfied with the appearance",
"ans_type": "Multiple choice",
"options": [
"No",
"Satisfied",
"a little",
"Very Satisfied"
]
],
"is_footer": true,
"is_header": true,
"display_type":
"ui": "single",
"randamization": true,
"pageno": true,
"skip": true,
"randomization": false
,
"category":
"id": "5a4167b5aa77271cb7f228ed",
"name": "Collect Feedback"
]
我已经写过这样的猫鼬查询：
Survey.find("_id":req.params.id, "start_datetime": "$lte": new Date(),"end_datetime": "$gt": new Date(),inv_users:1, inv_users:$elemMatch : cmp_user_id:user_id, function(err,survey)
if(survey)
res.json(survey);
else if(!survey)
res.json(
status:0,
message: "Survey doesn't exist!"
)
);
【问题讨论】：
【参考方案1】：你与投影混合匹配
inv_users:1
这在匹配中意味着仅匹配值为 1 的 inv_users。（您的意图可能是针对项目，但您询问的输出与此预测相矛盾）
还有，
$elemMatch 运算符将查询结果中的字段内容限制为仅包含与 $elemMatch 条件匹配的第一个元素。
这应该适用于您的情况
Survey.find(
"_id" : req.params.id,
"start_datetime": "$lte": new Date(),
"end_datetime" : "$gt": new Date(),
inv_users :
$elemMatch:
cmp_user_id: user_id
,
function (err, survey)
if (survey)
res.json(survey);
else if (!survey)
res.json(
status : 0,
message: "Survey doesn't exist!"
)
);
【讨论】：
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