结合更新和查询部分以在MongoDB中形成上色文档？
您需要将$set运算符与upsert：true一起使用。首先让我们创建一个包含文档的集合-
> db.updateWithUpsertDemo.insertOne({"StudentFirstName":"John","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2a61c345990cee87fd890")
}
> db.updateWithUpsertDemo.insertOne({"StudentFirstName":"Larry","StudentAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2a624345990cee87fd891")
}
> db.updateWithUpsertDemo.insertOne({"StudentFirstName":"David","StudentAge":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2a62c345990cee87fd892")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.updateWithUpsertDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd2a61c345990cee87fd890"),
"StudentFirstName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5cd2a624345990cee87fd891"),
"StudentFirstName" : "Larry",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cd2a62c345990cee87fd892"),
"StudentFirstName" : "David",
"StudentAge" : 24
}以下是结合了更新和查询部分以形成上色文档的查询-
> db.updateWithUpsertDemo.update({_id: ObjectId("5cd2a624345990cee87fd891")},{"$set": {"StudentFirstName": "Chris"}}, {upsert:true});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })让我们检查字段“StudentFirstName”是否已更改-
> db.updateWithUpsertDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd2a61c345990cee87fd890"),
"StudentFirstName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5cd2a624345990cee87fd891"),
"StudentFirstName" : "Chris",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cd2a62c345990cee87fd892"),
"StudentFirstName" : "David",
"StudentAge" : 24
}