MongoDB查询将匹配的键添加到查询后的列表？
为此，请aggregate()在MongoDB中使用。让我们创建一个包含文档的集合-
> db.demo334.insertOne({
... "Name": "Chris",
... "Age": 21,
... "details": [{
... "Subject": "MySQL",
... "Score": 78
... }, {
... "Subject": "MongoDB",
... "Score": 45
... }]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e52241bf8647eb59e562090")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo334.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e52241bf8647eb59e562090"),
"Name" : "Chris",
"Age" : 21,
"details" : [
{
"Subject" : "MySQL",
"Score" : 78
},
{
"Subject" : "MongoDB",
"Score" : 45
}
]
}以下是在查询后将匹配的键添加到列表的查询-
> db.demo334.aggregate([
... { $addFields: {
... details: {$filter: {
... input: '$details',
... as: 'out',
... cond: {$gte: ['$$out.Score',70 ]}
... }}
... }}
... ])这将产生以下输出-
{ "_id" : ObjectId("5e52241bf8647eb59e562090"), "Name" : "Chris", "Age" : 21, "details" : [ { "Subject" : "MySQL", "Score" : 78 } ] }