是否包括所有现有字段并在MongoDB中添加新字段以记录文档？
您可以借助$addFields运算符来实现。为了理解这个概念，让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.addFieldDemo.insertOne({"EmployeeId":101,"EmployeeName":"Larry","EmployeeDetails":{
"EmployeeSalary":65000,"EmployeeCity":"New York","Message":"Hi"}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c7f654d8d10a061296a3c44")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.addFieldDemo.find().pretty();
以下是输出-
{
"_id" : ObjectId("5c7f654d8d10a061296a3c44"),
"EmployeeId" : 101,
"EmployeeName" : "Larry",
"EmployeeDetails" : {
"EmployeeSalary" : 65000,
"EmployeeCity" : "New York",
"Message" : "Hi"
}
}这是包含所有现有字段并向MongoDB中的文档添加新字段的查询-
> db.addFieldDemo.aggregate([ { "$addFields": { "EmployeeBasicSalary":"$EmployeeDetails.EmployeeSalary" } } ]).pretty();以下是输出-
{
"_id" : ObjectId("5c7f654d8d10a061296a3c44"),
"EmployeeId" : 101,
"EmployeeName" : "Larry",
"EmployeeDetails" : {
"EmployeeSalary" : 65000,
"EmployeeCity" : "New York",
"Message" : "Hi"
},
"EmployeeBasicSalary" : 65000
}查看示例输出，已添加“EmployeeBasicSalary”。
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