MongoDB文档中如何过滤特定值
要过滤特定值，请在MongoDB中使用$filter。让我们创建一个包含文档的集合-
> db.demo751.insertOne(
... {
... _id: 101,
... details: [
... { Name: "Robert", id:110,Age:21},
... { Name: "Rae", id:110,Age:22},
... {Name: "Ralph", id:116,Age:23}
... ]
... }
... );
{ "acknowledged" : true, "insertedId" : 101 }在find()方法的帮助下显示集合中的所有文档-
> db.demo751.find().pretty();
这将产生以下输出-
{
"_id" : 101,
"details" : [
{
"Name" : "Robert",
"id" : 110,
"Age" : 21
},
{
"Name" : "Rae",
"id" : 110,
"Age" : 22
},
{
"Name" : "Ralph",
"id" : 116,
"Age" : 23
}
]
}以下是要过滤的查询-
> db.demo751.aggregate([
... {
... $addFields: {
... details: {
... $let: {
... vars: {
... filtered: { $filter: { input: "$details", as: "out", cond: { $eq: [ "$$out.id", 110 ] } } }
... },
... in: { $slice: [ "$$filtered", -1 ] }
... }
... }
... }
... }
... ])这将产生以下输出-
{ "_id" : 101, "details" : [ { "Name" : "Rae", "id" : 110, "Age" : 22 } ] }