to print nested json array values into csv using MongoDB - mongodb

Question

I want to output the nested json array into csv.
sample.json
{
"DocId":"ABC",
"User":[
{
"Id":1234,
"Username":"sam1234",
"Name":"Sam",
"ShippingAddress":{
"Address1":"123 Main St.",
"Address2":null,
"City":"Durham",
"State":"NC"
}
},
{
"Id":5678,
"Username":"sam5678",
"Name":"Sam",
"ShippingAddress":{
"Address1":"5678 Main St.",
"Address2":null,
"City":"Durham",
"State":"NC"
}
}
]
}
enter code here
Above is the sample file, DocID must not be printed, and output in csv must be only for array contents
Id Username Name ShippingAddress
1234 sam1234 Sam 123 Main St.Durham NC
5678 sam5678 Sam 5678 Main St.Durham NC
How to print with headers, and with out headers in csv

Answer 1

One way to do is to do it in two steps
Perform aggregation on this collection and change the structure of the collection docs and output them in another collection
Use mongoexport to export the collection created in step 1 as CSV [This step can be used directly ^-^].
For step 1, Lets say I have db -> test and collection -> stack, so aggregation query is:
db.stack.aggregate([
{ $unwind:"$User"},
{ $project : { Id : "$User.Id" , Username:"$User.Username", Name:"$User.Name", ShippingAddress:"$User.ShippingAddress", _id:0} },
{ $out: "result" }
])
For step 2, use mongoexport terminal utility:
mongoexport --db test --collection result --csv --fields "Id,Username,Name,ShippingAddress" --out file.csv