MongoDB $推入嵌套数组？
在这里，$push可用于在嵌套数组中添加新文档。为了理解上面的$push概念，让我们创建一个带有嵌套数组文档的集合。用于创建包含文档的集合的查询如下：
>db.nestedArrayDemo.insertOne({"EmployeeName":"Larry","EmployeeSalary":9000,"EmployeeDetails":
[{"EmployeeDOB":new Date('1990-01-21'),"EmployeeDepartment":"ComputerScience","EmployeeProject":
[{"Technology":"C","Duration":6},{"Technology":"Java","Duration":7}]}]});以下是输出：
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6d73090c3d5054b766a76e")
}现在，您可以借助find()方法显示集合中的文档。查询如下：
> db.nestedArrayDemo.find().pretty();
以下是输出：
{
"_id" : ObjectId("5c6d73090c3d5054b766a76e"),
"EmployeeName" : "Larry",
"EmployeeSalary" : 9000,
"EmployeeDetails" : [
{
"EmployeeDOB" : ISODate("1990-01-21T00:00:00Z"),
"EmployeeDepartment" : "ComputerScience",
"EmployeeProject" : [
{
"Technology" : "C",
"Duration" : 6
},
{
"Technology" : "Java",
"Duration" : 7
}
]
}
]
}这是嵌套数组中添加新文档的$push演示。查询如下：
>db.nestedArrayDemo.update({"_id":ObjectId("5c6d73090c3d5054b766a76e"),
"EmployeeDetails.EmployeeDepartment":"ComputerScience"}, {"$push":
{"EmployeeDetails.$.EmployeeProject": {"Technology":"Python", "Duration":4 }}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })在上面的查询中，我在嵌套数组中添加了一个文档{“Technology”：“Python”，“Duration”：4}。现在再次显示集合中的文档。查询如下：
> db.nestedArrayDemo.find().pretty();
以下是输出：
{
"_id" : ObjectId("5c6d73090c3d5054b766a76e"),
"EmployeeName" : "Larry",
"EmployeeSalary" : 9000,
"EmployeeDetails" : [
{
"EmployeeDOB" : ISODate("1990-01-21T00:00:00Z"),
"EmployeeDepartment" : "ComputerScience",
"EmployeeProject" : [
{
"Technology" : "C",
"Duration" : 6
},
{
"Technology" : "Java",
"Duration" : 7
},
{
"Technology" : "Python",
"Duration" : 4
}
]
}
]
}