如何在 MongoDB 中提取子数组值?
mongodbdatabasebig data analytics更新于 2026/1/19 5:22:17
要在 MongoDB 中提取子数组值，可以使用 $elemMatch 投影运算符。
首先，我们创建一个包含文档的集合 −
> db.extractSubArrayDemo.insertOne(
... {
... _id: 101,
... "clientName":"Larry",
... "ClientDetails":
... [
... {
... "ClientProjectName":"Online Game",
... "DeveloperTeamSize": 10
... },
... {
... "ClientProjectName":"Pig Dice Game",
... "DeveloperTeamSize": 12
... },
... {
... "ClientProjectName":"Web Student Tracker",
... "DeveloperTeamSize": 11
... }
...
... ]
... }
... );
{ "acknowledged" : true, "insertedId" : 101 }
以下是使用 find() 方法显示集合中的所有文档的查询 −
> db.extractSubArrayDemo.find().pretty();
这将产生以下输出 −
{
"_id" : 101,
"clientName" : "Larry",
"ClientDetails" : [
{
"ClientProjectName" : "Online Game",
"DeveloperTeamSize" : 10
},
{
"ClientProjectName" : "Pig Dice Game",
"DeveloperTeamSize" : 12
},
{
"ClientProjectName" : "Web Student Tracker",
"DeveloperTeamSize" : 11
}
]
}
以下是在 MongoDB 中提取子数组值的查询 −
> db.extractSubArrayDemo.find({ '_id': 101 },{ _id: 0, ClientDetails:
{ $elemMatch: {ClientProjectName: 'Pig Dice Game' } }}).pretty();
这将产生以下输出 −
{
"ClientDetails" : [
{
"ClientProjectName" : "Pig Dice Game",
"DeveloperTeamSize" : 12
}
]
}
