Mongodb aggregate with cond and query value - mongodb

Question

I'm new to mongodb. I need to know how it is possible to query item for set to the value with aggregate
Data
[
{
"_id" : "11111",
"parent_id" : "99",
"name" : "AAAA"
},
{
"_id" : "11112",
"parent_id" : "99",
"name" : "BBBB"
},
{
"_id" : "11113",
"parent_id" : "100",
"name" : "CCCC"
},
{
"_id" : "11114",
"parent_id" : "99",
"name" : "DDDD"
}
]
mongoshell
Assume $check is false
db.getCollection('test').aggregate(
[
{
"$group": {
"_id": "$id",
//...,
"item": {
"$last": {
"$cond": [
{"$eq": ["$check", true]},
"YES",
* * ANSWER **,
}
]
}
},
}
]
)
So i need the result for item is all the name contain with same parent_id as string of array
Expect result
[
{
"_id" : "11111",
"parent_id" : "99",
"name" : "AAAA",
"item" : ["AAAA","BBBB","DDDD"]
},
{
"_id" : "11112",
"parent_id" : "99",
"name" : "BBBB",
"item" : ["AAAA","BBBB","DDDD"]
},
{
"_id" : "11113",
"parent_id" : "100",
"name" : "CCCC",
"item" : ["CCCC"]
},
{
"_id" : "11114",
"parent_id" : "99",
"name" : "DDDD",
"item" : ["AAAA","BBBB","DDDD"]
}
]

Answer 1

Try this..
Sample live demo
db.collection.aggregate([
{
"$group": {
"_id": "$parent_id",
"item": {
"$push": "$name"
},
"data": {
"$push": {
"_id": "$_id",
"name": "$name"
}
}
}
},
{
"$unwind": "$data"
},
{
"$project": {
"_id": "$data._id",
"parent_id": "$_id",
"name": "$data.name",
"item": 1
}
}
])