MongoDB查询以查找并返回具有条件的子文档？
让我们创建一个包含文档的集合-
> db.demo345.insertOne({
... "UserName" : "Robert",
... "UserDetails" : [
... {
... "isMarried" : false,
... "CountryName":"US"
...
... },
... {
... "isMarried" : true,
... "CountryName":"UK"
...
... },
... {
... "isMarried" : false,
... "CountryName":"AUS"
...
... }
... ]
... }
... )
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5404fdf8647eb59e5620ac")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo345.find();
这将产生以下输出-
{
"_id" : ObjectId("5e5404fdf8647eb59e5620ac"), "UserName" : "Robert", "UserDetails" : [
{ "isMarried" : false, "CountryName" : "US" },
{ "isMarried" : true, "CountryName" : "UK" },
{ "isMarried" : false, "CountryName" : "AUS" }
]
}以下是查找并返回带有条件的子文档的查询-
> db.demo345.aggregate([
... {
... $match: { UserName: "Robert" }
... },
... {
... $addFields: {
... UserDetails: {
... $filter: {
... input: "$UserDetails",
... cond: {
... $eq: [ "$$this.isMarried", true ]
... }
... }
... }
... }
... }
... ])这将产生以下输出-
{
"_id" : ObjectId("5e5404fdf8647eb59e5620ac"), "UserName" : "Robert", "UserDetails" : [
{ "isMarried" : true, "CountryName" : "UK" }
]
}