如何基于名称列表在MongoDB查询结果中获取标签计数？
您可以使用$in运算符。首先让我们创建一个包含文档的集合-
> db.tagCountDemo.insertOne({"ListOfNames":["John","Sam","Carol"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd64b387924bb85b3f48944")
}
> db.tagCountDemo.insertOne({"ListOfNames":["Bob","David","John"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd64b4b7924bb85b3f48945")
}
> db.tagCountDemo.insertOne({"ListOfNames":["Mike","Robert","Chris"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd64b5d7924bb85b3f48946")
}
> db.tagCountDemo.insertOne({"ListOfNames":["James","Carol","Jace"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd64b717924bb85b3f48947")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.tagCountDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd64b387924bb85b3f48944"),
"ListOfNames" : [
"John",
"Sam",
"Carol"
]
}
{
"_id" : ObjectId("5cd64b4b7924bb85b3f48945"),
"ListOfNames" : [
"Bob",
"David",
"John"
]
}
{
"_id" : ObjectId("5cd64b5d7924bb85b3f48946"),
"ListOfNames" : [
"Mike",
"Robert",
"Chris"
]
}
{
"_id" : ObjectId("5cd64b717924bb85b3f48947"),
"ListOfNames" : [
"James",
"Carol",
"Jace"
]
}以下是在MongoDB中获取标签计数的查询
> db.tagCountDemo.find({"ListOfNames":{$in:['John','Carol']}});这将产生以下输出-
{ "_id" : ObjectId("5cd64b387924bb85b3f48944"), "ListOfNames" : [ "John", "Sam", "Carol" ] }
{ "_id" : ObjectId("5cd64b4b7924bb85b3f48945"), "ListOfNames" : [ "Bob", "David", "John" ] }
{ "_id" : ObjectId("5cd64b717924bb85b3f48947"), "ListOfNames" : [ "James", "Carol", "Jace" ] }