MongoDB中如何实现数组匹配？
使用$all进行数组匹配。$all运算符选择字段值是包含所有指定元素的数组的文档。让我们用文档创建一个集合-
> db.demo668.createIndex({"ListOfSubject":1});
{
"createdCollectionAutomatically" : true,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}
> db.demo668.insert({"ListOfSubject":["MySQL","Java","C"]});
WriteResult({ "nInserted" : 1 })
> db.demo668.insert({"ListOfSubject":["MongoDB","Python","C++"]});
WriteResult({ "nInserted" : 1 })
> db.demo668.insert({"ListOfSubject":["C#","Spring","Hibernate","MongoDB"]});
WriteResult({ "nInserted" : 1 })在find()方法的帮助下显示集合中的所有文档-
> db.demo668.find();
这将产生以下输出-
{ "_id" : ObjectId("5ea311df04263e90dac943d6"), "ListOfSubject" : [ "MySQL", "Java", "C" ] }
{ "_id" : ObjectId("5ea311e004263e90dac943d7"), "ListOfSubject" : [ "MongoDB", "Python", "C++" ] }
{ "_id" : ObjectId("5ea311e104263e90dac943d8"), "ListOfSubject" : [ "C#", "Spring", "Hibernate", "MongoDB" ] }以下是数组匹配的查询-
> db.demo668.find({"ListOfSubject":{ $all:["MongoDB","C++"]}});这将产生以下输出-
{ "_id" : ObjectId("5ea311e004263e90dac943d7"), "ListOfSubject" : [ "MongoDB", "Python", "C++" ] }