如何在MongoDB中的数组中获取匹配的文档？
要获取匹配的文档，请使用$elemMatch。首先让我们创建一个包含文档的集合-
> db.getMatchingDocumentDemo.insertOne(
{
_id :1,
"UserDetails":[
{
"UserName":"John",
"UserAge":23
}
]
}
);
{ "acknowledged" : true, "insertedId" : 1 }
> db.getMatchingDocumentDemo.insertOne( { _id :2, "UserDetails":[ { "UserName":"Larry", "UserAge":24 } ] } );
{ "acknowledged" : true, "insertedId" : 2 }以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.getMatchingDocumentDemo.find().pretty();
这将产生以下输出-
{
"_id" : 1,
"UserDetails" : [
{
"UserName" : "John",
"UserAge" : 23
}
]
}
{
"_id" : 2,
"UserDetails" : [
{
"UserName" : "Larry",
"UserAge" : 24
}
]
}以下是在MongoDB中的数组中获取匹配文档的查询-
> db.getMatchingDocumentDemo.find({UserDetails: {$elemMatch: {UserAge: 24}}});这将产生以下输出-
{ "_id" : 2, "UserDetails" : [ { "UserName" : "Larry", "UserAge" : 24 } ] }