ให้เราสร้างคอลเลกชันที่มีเอกสารก่อน -
> db.demo389.insertOne(
... {
... "details":[
... {
... "Name":[
... "Chris",
... "David"
... ]
... },
... {
... "Name":[
... "Bob",
... "Mike"
... ]
... },
... {
... "Name":[
... "Carol",
... "Sam"
... ]
... },
... {
... "Name":[
... "David",
... "John"
... ]
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5d1d8f22064be7ab44e7f9")
} แสดงเอกสารทั้งหมดจากคอลเล็กชันโดยใช้วิธี find() -
> db.demo389.find();
สิ่งนี้จะสร้างผลลัพธ์ต่อไปนี้ -
{
"_id" : ObjectId("5e5d1d8f22064be7ab44e7f9"), "details" : [
{ "Name" : [ "Chris", "David" ] }, { "Name" : [ "Bob", "Mike" ] },
{ "Name" : [ "Carol", "Sam" ] }, { "Name" : [ "David", "John" ] }
]
} ต่อไปนี้เป็นแบบสอบถามเพื่อดึงค่าทั้งหมด -
> db.demo389.aggregate([
... {
... $unwind: "$details"
... },
... {
... $unwind: "$details.Name"
... },
... {
... $project: {
... "_id": "$_id",
... "Name": "$details.Name"
... }
... },
... {
... $group: {
... _id: "_id",
... out: {
... $push: "$Name"
... }
... }
... },
... {
... $project: {
... "_id": 0,
... "NameArray": "$out"
... }
... }
... ]) สิ่งนี้จะสร้างผลลัพธ์ต่อไปนี้ -
{ "NameArray" : [ "Chris", "David", "Bob", "Mike", "Carol", "Sam", "David", "John" ] } 