I only want to see matching documents, i.e. only T3 in the example below. I can find the matching documents between lotterytickets
(many documents) and lotterydrawing
(only a few documents).
How can I filter out the non-matching documents? Basically, I’d not like to see documents with the condition drawnticket==[]
, but I haven’t found the conditional code to apply.
Any help would be appreciated. Thank you in advance
Configuration:
db={
"lotteryticket": [
{
"_id": ObjectId("6021ce0cb4d2c2b4f24c3a2e"),
"ticket": "T1",
"player": "Alice"
},
{
"_id": ObjectId("6021ce0cb4d2c2b4f24c3a2f"),
"ticket": "T2",
"player": "Bob"
},
{
"_id": ObjectId("6021ce0cb4d2c2b4f24c3a33"),
"ticket": "T3",
"player": "Charles"
}
],
"lotterydrawing": [
{
"_id": ObjectId("63309480b749b733c087b758"),
"ticket": "T3"
},
{
"_id": ObjectId("63309480b749b733c087b759"),
"ticket": "T9"
},
{
"_id": ObjectId("63309480b749b733c087b75a"),
"ticket": "T77"
}
]
}
Query:
db.lotteryticket.aggregate([
{
$lookup: {
from: "lotterydrawing",
localField: "ticket",
foreignField: "ticket",
as: "drawnticket",
}
}
])
Result:
[
{
"_id": ObjectId("6021ce0cb4d2c2b4f24c3a2e"),
"drawnticket": [],
"player": "Alice",
"ticket": "T1"
},
{
"_id": ObjectId("6021ce0cb4d2c2b4f24c3a2f"),
"drawnticket": [],
"player": "Bob",
"ticket": "T2"
},
{
"_id": ObjectId("6021ce0cb4d2c2b4f24c3a33"),
"drawnticket": [
{
"_id": ObjectId("63309480b749b733c087b758"),
"ticket": "T3"
}
],
"player": "Charles",
"ticket": "T3"
}
]
2
Answers
Add a match stage, to filter stages with the empty drawn tickets. Like this:
Playground.
try this query
Playground.