使用MongoDB查询数组内的嵌套字段
要查询数组中的嵌套字段，请在MongoDB中使用$elemMatch。让我们创建一个包含文档的集合-
> db.demo153.insertOne({"ClientDetails":[{"ClientName":"Chris","ClientProject":"Online Banking System"},{"ClientName":"David","ClientProject":"Online School Management"}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e351957fdf09dd6d08539df")
}
> db.demo153.insertOne({"ClientDetails":[{"ClientName":"Carol","ClientProject":"Online Book System"},{"ClientName":"Mike","ClientProject":"Game Development"}]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3519c9fdf09dd6d08539e0")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo153.find();
这将产生以下输出-
{
"_id" : ObjectId("5e351957fdf09dd6d08539df"), "ClientDetails" : [
{ "ClientName" : "Chris", "ClientProject" : "Online Banking System" },
{ "ClientName" : "David", "ClientProject" : "Online School Management" }
]
}
{
"_id" : ObjectId("5e3519c9fdf09dd6d08539e0"), "ClientDetails" : [
{ "ClientName" : "Carol", "ClientProject" : "Online Book System" },
{ "ClientName" : "Mike", "ClientProject" : "Game Development" }
]
}以下是如何查询数组内的嵌套字段-
> db.demo153.find({"ClientDetails": { "$elemMatch" : {"ClientProject": { "$in": ["Online Banking System"] } } } });这将产生以下输出-
{ "_id" : ObjectId("5e351957fdf09dd6d08539df"), "ClientDetails" : [ { "ClientName" : "Chris", "ClientProject" : "Online Banking System" }, { "ClientName" : "David", "ClientProject" : "Online School Management" } ] }