如何在MongoDB中向现有记录添加字段？
您可以使用update命令将字段添加到现有记录。首先让我们创建一个包含文档的集合-
> db.addAFieldToEveryRecordDemo.insertOne({"ClientName":"Chris","ClientAge":34});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd00e32588d4a6447b2e061")
}
> db.addAFieldToEveryRecordDemo.insertOne({"ClientName":"Robert","ClientAge":36});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd00e59588d4a6447b2e062")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.addAFieldToEveryRecordDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd00e32588d4a6447b2e061"),
"ClientName" : "Chris",
"ClientAge" : 34
}
{
"_id" : ObjectId("5cd00e59588d4a6447b2e062"),
"ClientName" : "Robert",
"ClientAge" : 36
}这是向每个记录添加字段的查询。我们正在添加ClientDetails-
>db.addAFieldToEveryRecordDemo.update({},{$set:{"ClientDetails.ClientCountryName":""}},true,true);
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })让我们检查所有文档是否已添加新记录-
> db.addAFieldToEveryRecordDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd00e32588d4a6447b2e061"),
"ClientName" : "Chris",
"ClientAge" : 34,
"ClientDetails" : {
"ClientCountryName" : ""
}
}
{
"_id" : ObjectId("5cd00e59588d4a6447b2e062"),
"ClientName" : "Robert",
"ClientAge" : 36,
"ClientDetails" : {
"ClientCountryName" : ""
}
}