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Legal Studies我想在一個已經建立的文件中建立一個新欄位。如何使用 MongoDB 查詢來完成這項操作？
使用 $addToSet 在 MongoDB 中建立一個新欄位。讓我們首先使用文件建立集合 -
> db.createFieldDemo.insertOne({"StudentFirstName":"John","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e28b50a6c6dd317ad95")
}
> db.createFieldDemo.insertOne({"StudentFirstName":"Larry","StudentAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e2fb50a6c6dd317ad96")
}
> db.createFieldDemo.insertOne({"StudentFirstName":"Chris","StudentAge":22});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e38b50a6c6dd317ad97")
}
> db.createFieldDemo.insertOne({"StudentFirstName":"David","StudentAge":25});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd99e43b50a6c6dd317ad98")
}以下查詢使用 find() 方法顯示集合中的所有文件 -
> db.createFieldDemo.find().pretty();
這將生成以下輸出 -
{
"_id" : ObjectId("5cd99e28b50a6c6dd317ad95"),
"StudentFirstName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5cd99e2fb50a6c6dd317ad96"),
"StudentFirstName" : "Larry",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cd99e38b50a6c6dd317ad97"),
"StudentFirstName" : "Chris",
"StudentAge" : 22
}
{
"_id" : ObjectId("5cd99e43b50a6c6dd317ad98"),
"StudentFirstName" : "David",
"StudentAge" : 25
}以下查詢用於建立一個新欄位。在此，我們建立一個欄位“StudentLastName” -
> db.createFieldDemo.update({_id: ObjectId("5cd99e43b50a6c6dd317ad98")}, {$addToSet: {"StudentLastName": "Miller"}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })讓我們檢查上述集合中的所有文件 -
> db.createFieldDemo.find().pretty();
這將生成以下輸出 -
{
"_id" : ObjectId("5cd99e28b50a6c6dd317ad95"),
"StudentFirstName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5cd99e2fb50a6c6dd317ad96"),
"StudentFirstName" : "Larry",
"StudentAge" : 23
}
{
"_id" : ObjectId("5cd99e38b50a6c6dd317ad97"),
"StudentFirstName" : "Chris",
"StudentAge" : 22
}
{
"_id" : ObjectId("5cd99e43b50a6c6dd317ad98"),
"StudentFirstName" : "David",
"StudentAge" : 25,
"StudentLastName" : [
"Miller"
]
}
更新於： 30-Jul-2019
63 次瀏覽
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