查询MongoDB中的数组数组？
使用$in运算符查询MongoDB中的数组数组。为了理解这个概念，让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.arrayOfArraysDemo.insertOne({"EmployeeName":"Larry","EmployeeSkills":[["Java","MongoDB","MySQL","SQL Server"]]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c7f7a8d8d10a061296a3c5b")
}
> db.arrayOfArraysDemo.insertOne({"EmployeeName":"Mike","EmployeeSkills":[["C","C++"]]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c7f7aa68d10a061296a3c5c")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.arrayOfArraysDemo.find().pretty();
以下是输出-
{
"_id" : ObjectId("5c7f7a8d8d10a061296a3c5b"),
"EmployeeName" : "Larry",
"EmployeeSkills" : [
[
"Java",
"MongoDB",
"MySQL",
"SQL Server"
]
]
}
{
"_id" : ObjectId("5c7f7aa68d10a061296a3c5c"),
"EmployeeName" : "Mike",
"EmployeeSkills" : [
[
"C",
"C++"
]
]
}这是查询MongoDB中的数组数组的查询-
> db.arrayOfArraysDemo.find({'EmployeeSkills':{$elemMatch:{$elemMatch:{$in:['MongoDB']}}}
}).pretty();以下是输出-
{
"_id" : ObjectId("5c7f7a8d8d10a061296a3c5b"),
"EmployeeName" : "Larry",
"EmployeeSkills" : [
[
"Java",
"MongoDB",
"MySQL",
"SQL Server"
]
]
}