如何删除MongoDB中的关键字段？
要删除MongoFB中的关键字段，您可以使用$unset运算符。让我们首先创建一个包含文档的集合-
>db.removeKeyFieldsDemo.insertOne({"StudentFirstName":"John","StudentLastName":"Doe","StudentAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cc6c8289cb58ca2b005e672")
}
>db.removeKeyFieldsDemo.insertOne({"StudentFirstName":"John","StudentLastName":"Smith","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cc6c8359cb58ca2b005e673")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.removeKeyFieldsDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cc6c8289cb58ca2b005e672"),
"StudentFirstName" : "John",
"StudentLastName" : "Doe",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cc6c8359cb58ca2b005e673"),
"StudentFirstName" : "John",
"StudentLastName" : "Smith",
"StudentAge" : 21
}以下是删除关键字段的查询。在这里，我们正在删除StudentAge-
> db.removeKeyFieldsDemo.updateMany({},{$unset:{StudentAge:1}});
{ "acknowledged" : true, "matchedCount" : 2, "modifiedCount" : 2 }让我们显示上述集合中的所有文档-
> db.removeKeyFieldsDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cc6c8289cb58ca2b005e672"),
"StudentFirstName" : "John",
"StudentLastName" : "Doe"
}
{
"_id" : ObjectId("5cc6c8359cb58ca2b005e673"),
"StudentFirstName" : "John",
"StudentLastName" : "Smith"
}