Change a Document更改文档

Overview概述

You can change documents in a MongoDB collection using either update or replace operations. 您可以使用更新或替换操作更改MongoDB集合中的文档。Update operations mutate specified fields in one or more documents and leave other fields and values unchanged. 更新操作会更改一个或多个文档中的指定字段，并保持其他字段和值不变。Replace operations remove all existing fields in one or more documents and substitute them with specified fields and values.替换操作将删除一个或多个文档中的所有现有字段，并用指定的字段和值替换它们。

Update更新

To perform an update to one or more documents, create an update document that specifies the update operator (the type of update to perform) and the fields and values that describe the change. 要对一个或多个文档执行更新，请创建一个更新文档，指定更新运算符（要执行的更新类型）以及描述更改的字段和值。Update documents use the following format:使用以下格式更新文档：

{
   <update operator>: {
      <field> : {
         ...
      },
      <field> : {
      }
   },
   <update operator>: {
      ...
   }
}

The top level of an update document contains one or more of the following update operators:更新文档的顶层包含以下一个或多个更新运算符：

• $set: replaces the value of a field with a specified one：将字段的值替换为指定的值
• $inc: increments or decrements field values：递增或递减字段值
• $rename: renames fields：重命名字段
• $unset: removes fields：删除字段
• $mul: multiplies a field value by a specified number：将字段值乘以指定的数字

See the MongoDB Server manual for a complete list of update operators and their usage.有关更新运算符及其用法的完整列表，请参阅MongoDB Server手册。

The update operators apply only to the fields associated with them in your update document.更新运算符仅应用于更新文档中与其关联的字段。

{
   _id: 465,
   item: "Hand-thrown ceramic plate",
   price: 32.50,
   quantity: 7,
}

const myDB = client.db("myDB");
const myColl = myDB.collection("items");

const filter = { _id: 465 };

// update the value of the 'quantity' field to 5将“数量”字段的值更新为5
const updateDocument = {
   $set: {
      quantity: 5,
   },
};
const result = await myColl.updateOne(filter, updateDocument);

{
   _id: 465,
   item: "Hand-thrown ceramic plate",
   price: 32.50,
   quantity: 5,
}

Replace替换

To perform a replacement operation, create a replacement document that consists of the fields and values that you would like to use in your replace operation. 若要执行替换操作，请创建一个替换文档，该文档由要在替换操作中使用的字段和值组成。Replacement documents use the following format:替换文件使用以下格式：

{
   <field>: {
      <value>
   },
   <field>: {
      ...
   }
}

Replacement documents are the documents that you want to take the place of existing documents that match the query filters.替换文档是要替换与查询筛选器匹配的现有文档的文档。

{
   _id: 501,
   item: "3-wick beeswax candle",
   price: 18.99,
   quantity: 10,
}

const myDB = client.db("myDB");
const myColl = myDB.collection("items");

const filter = { _id: 501 };

// replace the matched document with the replacement document用替换文档替换匹配的文档
const replacementDocument = {
   item: "Vintage silver flatware set",
   price: 79.15,
   quantity: 1,
};
const result = await myColl.replaceOne(filter, replacementDocument);

{
   _id: 501,
   item: "Vintage silver flatware set",
   price: 79.15,
   quantity: 1,
}