在MongoDB中提取子数组值？
要在MongoDB中提取子数组值，可以使用$elemMatch投影运算符。
首先让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 }以下是在find()方法的帮助下显示集合中所有文档的查询-
> 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
}
]
}