Arrays 多个集合上的MongoDB客户端联接
我的收藏 预订-id,unitId 单位-id、标题、课程id 课程-id,标题 我想获得带有单元和课程标题的预订阵列,如下所示 博金·身份证单元·职称课程·职称 xxxx ABC XYZ 我当前的代码Arrays 多个集合上的MongoDB客户端联接,arrays,mongodb,mongodb-query,aggregation-framework,Arrays,Mongodb,Mongodb Query,Aggregation Framework,我的收藏 预订-id,unitId 单位-id、标题、课程id 课程-id,标题 我想获得带有单元和课程标题的预订阵列,如下所示 博金·身份证单元·职称课程·职称 xxxx ABC XYZ 我当前的代码 const bookings = await db.getDB().collection('bookings').aggregate([ { $lookup: { from: 'courseUnit', localField: 'courseUni
const bookings = await db.getDB().collection('bookings').aggregate([
{
$lookup:
{
from: 'courseUnit',
localField: 'courseUnitId',
foreignField: '_id',
as: 'uu'
}
},
{
$unwind:"$uu"
}
]).toArray();
您正在寻找的解决方案是通过在聚合管道中使用多时间
$lookup
管道来解决的。e、 g:
db.Bookings.aggregate([
{
"$lookup" :
{"from": "Unit", "localField": "unitId", "foreignField": "_id", as : "UnitDetails" }
},
{
"$unwind" : "$UnitDetails"
},
{
$lookup:
{ "from": "Course", "localField": "UnitDetails.courseId", "foreignField": "_id", as: "CouserDetails" }
},
{
"$unwind" : "$CouserDetails"
},
{
$project: {_id:0, "Boking_id" : "$_id", "Unit_title": "$UnitDetails.title", "course_title": "$CouserDetails.title" }
}
]).pretty()
上述查询的输出如下:
{
"Boking_id" : ObjectId("5dff07e4187da4c2b5ffc59f"),
"Unit_title" : "unit title for course title 3",
"course_title" : "Title of the Course collection 3"
}
> db.Bookings2.find()
{ "_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"), "unitId" : "5dff66c9187da4c2b5ffc5a2" }
> db.Unit2.find()
{ "_id" : ObjectId("5dff66c9187da4c2b5ffc5a2"), "title" : "Unit title 1", "courseId" : "5dff6694187da4c2b5ffc5a0" }
> db.Course2.find()
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a0"), "title" : "Title of the Course collection 1" }
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a1"), "title" : "Title of the Course collection 2" }
>
> db.Bookings2.aggregate([ {$project: {"unitObjectId" : {$toObjectId: "$unitId"}} }, {$lookup: {"from": "Unit2", "localField": "unitObjectId", "foreignField": "_id", as: "UnitDetails" } }, {$unwind: "$UnitDetails"}, {$project: {"courseObjectId": {$toObjectId: "$UnitDetails.courseId" }, "unitTitle": "$UnitDetails.title" } }, {$lookup: {"from": "Course2", "localField": "courseObjectId", "foreignField": "_id", as: "Course2Details" } }, {$unwind: "$Course2Details"}, {$project: {_id: 0, "Boking_id": "$_id", "Unit_title": "$unitTitle", "course_title": "$Course2Details.title" } } ]).pretty()
{
"Boking_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"),
"Unit_title" : "Unit title 1",
"course_title" : "Title of the Course collection 1"
}
>
在所有三个集合中,我的初始集合数据集如下所示:
> db.Bookings.find()
{ "_id" : ObjectId("5dff07e4187da4c2b5ffc59f"), "unitId" : ObjectId("5dff06d6187da4c2b5ffc59e") }
> db.Unit.find()
{ "_id" : ObjectId("5dff06d6187da4c2b5ffc59e"), "title" : "unit title for course title 3", "courseId" : ObjectId("5dff010d187da4c2b5ffc59b") }
> db.Course.find()
{ "_id" : ObjectId("5dff0108187da4c2b5ffc599"), "title" : "Title of the Course collection" }
{ "_id" : ObjectId("5dff010b187da4c2b5ffc59a"), "title" : "Title of the Course collection 2" }
{ "_id" : ObjectId("5dff010d187da4c2b5ffc59b"), "title" : "Title of the Course collection 3" }
{ "_id" : ObjectId("5dff010f187da4c2b5ffc59c"), "title" : "Title of the Course collection 4" }
>
有关详细信息,请参阅以下参考资料:
如果Unit&Course集合中unitId和courseId的值存储为简单字符串,则必须使用。我创建了另一组集合,并使用了$toObjectId
,如下所示:
{
"Boking_id" : ObjectId("5dff07e4187da4c2b5ffc59f"),
"Unit_title" : "unit title for course title 3",
"course_title" : "Title of the Course collection 3"
}
> db.Bookings2.find()
{ "_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"), "unitId" : "5dff66c9187da4c2b5ffc5a2" }
> db.Unit2.find()
{ "_id" : ObjectId("5dff66c9187da4c2b5ffc5a2"), "title" : "Unit title 1", "courseId" : "5dff6694187da4c2b5ffc5a0" }
> db.Course2.find()
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a0"), "title" : "Title of the Course collection 1" }
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a1"), "title" : "Title of the Course collection 2" }
>
> db.Bookings2.aggregate([ {$project: {"unitObjectId" : {$toObjectId: "$unitId"}} }, {$lookup: {"from": "Unit2", "localField": "unitObjectId", "foreignField": "_id", as: "UnitDetails" } }, {$unwind: "$UnitDetails"}, {$project: {"courseObjectId": {$toObjectId: "$UnitDetails.courseId" }, "unitTitle": "$UnitDetails.title" } }, {$lookup: {"from": "Course2", "localField": "courseObjectId", "foreignField": "_id", as: "Course2Details" } }, {$unwind: "$Course2Details"}, {$project: {_id: 0, "Boking_id": "$_id", "Unit_title": "$unitTitle", "course_title": "$Course2Details.title" } } ]).pretty()
{
"Boking_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"),
"Unit_title" : "Unit title 1",
"course_title" : "Title of the Course collection 1"
}
>
您正在寻找的解决方案是通过在聚合管道中使用多时间
$lookup
管道来解决的。e、 g:
db.Bookings.aggregate([
{
"$lookup" :
{"from": "Unit", "localField": "unitId", "foreignField": "_id", as : "UnitDetails" }
},
{
"$unwind" : "$UnitDetails"
},
{
$lookup:
{ "from": "Course", "localField": "UnitDetails.courseId", "foreignField": "_id", as: "CouserDetails" }
},
{
"$unwind" : "$CouserDetails"
},
{
$project: {_id:0, "Boking_id" : "$_id", "Unit_title": "$UnitDetails.title", "course_title": "$CouserDetails.title" }
}
]).pretty()
上述查询的输出如下:
{
"Boking_id" : ObjectId("5dff07e4187da4c2b5ffc59f"),
"Unit_title" : "unit title for course title 3",
"course_title" : "Title of the Course collection 3"
}
> db.Bookings2.find()
{ "_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"), "unitId" : "5dff66c9187da4c2b5ffc5a2" }
> db.Unit2.find()
{ "_id" : ObjectId("5dff66c9187da4c2b5ffc5a2"), "title" : "Unit title 1", "courseId" : "5dff6694187da4c2b5ffc5a0" }
> db.Course2.find()
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a0"), "title" : "Title of the Course collection 1" }
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a1"), "title" : "Title of the Course collection 2" }
>
> db.Bookings2.aggregate([ {$project: {"unitObjectId" : {$toObjectId: "$unitId"}} }, {$lookup: {"from": "Unit2", "localField": "unitObjectId", "foreignField": "_id", as: "UnitDetails" } }, {$unwind: "$UnitDetails"}, {$project: {"courseObjectId": {$toObjectId: "$UnitDetails.courseId" }, "unitTitle": "$UnitDetails.title" } }, {$lookup: {"from": "Course2", "localField": "courseObjectId", "foreignField": "_id", as: "Course2Details" } }, {$unwind: "$Course2Details"}, {$project: {_id: 0, "Boking_id": "$_id", "Unit_title": "$unitTitle", "course_title": "$Course2Details.title" } } ]).pretty()
{
"Boking_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"),
"Unit_title" : "Unit title 1",
"course_title" : "Title of the Course collection 1"
}
>
在所有三个集合中,我的初始集合数据集如下所示:
> db.Bookings.find()
{ "_id" : ObjectId("5dff07e4187da4c2b5ffc59f"), "unitId" : ObjectId("5dff06d6187da4c2b5ffc59e") }
> db.Unit.find()
{ "_id" : ObjectId("5dff06d6187da4c2b5ffc59e"), "title" : "unit title for course title 3", "courseId" : ObjectId("5dff010d187da4c2b5ffc59b") }
> db.Course.find()
{ "_id" : ObjectId("5dff0108187da4c2b5ffc599"), "title" : "Title of the Course collection" }
{ "_id" : ObjectId("5dff010b187da4c2b5ffc59a"), "title" : "Title of the Course collection 2" }
{ "_id" : ObjectId("5dff010d187da4c2b5ffc59b"), "title" : "Title of the Course collection 3" }
{ "_id" : ObjectId("5dff010f187da4c2b5ffc59c"), "title" : "Title of the Course collection 4" }
>
有关详细信息,请参阅以下参考资料:
如果Unit&Course集合中unitId和courseId的值存储为简单字符串,则必须使用。我创建了另一组集合,并使用了$toObjectId
,如下所示:
{
"Boking_id" : ObjectId("5dff07e4187da4c2b5ffc59f"),
"Unit_title" : "unit title for course title 3",
"course_title" : "Title of the Course collection 3"
}
> db.Bookings2.find()
{ "_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"), "unitId" : "5dff66c9187da4c2b5ffc5a2" }
> db.Unit2.find()
{ "_id" : ObjectId("5dff66c9187da4c2b5ffc5a2"), "title" : "Unit title 1", "courseId" : "5dff6694187da4c2b5ffc5a0" }
> db.Course2.find()
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a0"), "title" : "Title of the Course collection 1" }
{ "_id" : ObjectId("5dff6694187da4c2b5ffc5a1"), "title" : "Title of the Course collection 2" }
>
> db.Bookings2.aggregate([ {$project: {"unitObjectId" : {$toObjectId: "$unitId"}} }, {$lookup: {"from": "Unit2", "localField": "unitObjectId", "foreignField": "_id", as: "UnitDetails" } }, {$unwind: "$UnitDetails"}, {$project: {"courseObjectId": {$toObjectId: "$UnitDetails.courseId" }, "unitTitle": "$UnitDetails.title" } }, {$lookup: {"from": "Course2", "localField": "courseObjectId", "foreignField": "_id", as: "Course2Details" } }, {$unwind: "$Course2Details"}, {$project: {_id: 0, "Boking_id": "$_id", "Unit_title": "$unitTitle", "course_title": "$Course2Details.title" } } ]).pretty()
{
"Boking_id" : ObjectId("5dff6c2a187da4c2b5ffc5a3"),
"Unit_title" : "Unit title 1",
"course_title" : "Title of the Course collection 1"
}
>
@NEET,注意单元集合
courseId
的ObjectId值,而不仅仅是字符串,这就是为什么我提供了引用。如果您有简单字符串,请按照引用解决问题。单元中的courseId是字符串,但它当然是指_idcollection@NEETJASSI上述答案是否解决了您的问题?@NEETJASSI考虑了单位中courseId的字符串值,并更新了以前的答案,希望此查询能够解决您的问题。@NEET,请注意单位集合courseId
的ObjectId值,而不仅仅是字符串,这就是为什么我提供了引用,如果你有简单的字符串,那么按照引用来解决这个问题。单位中的courseId是字符串,但它对_id的引用是collection@NEETJASSI上述答案是否解决了您的问题?@NEETJASSI考虑了courseId的字符串值(单位),并更新了之前的答案,希望这个问题能解决你的问题。