如何使用MongoDB $ pull删除数组中的文档？
您需要与$pull运算符一起使用update命令来删除数组中的文档。让我们创建包含文档的集合。以下是查询
> db.deleteDocumentsDemo.insertOne(
... {
... "_id":100,
... "StudentsDetails" : [
... {
... "StudentId" : 1,
... "StudentName" : "John"
... },
... {
... "StudentId" : 2,
... "StudentName" : "Carol"
... },
... {
... "StudentId" : 3,
... "StudentName" : "Sam"
... },
... {
... "StudentId" : 4,
... "StudentName" : "Mike"
... }
... ]
... }
...
... );
{ "acknowledged" : true, "insertedId" : 100 }
> db.deleteDocumentsDemo.insertOne(
... {
... "_id":200,
... "StudentsDetails" : [
... {
... "StudentId" : 5,
... "StudentName" : "David"
... },
... {
... "StudentId" : 6,
... "StudentName" : "Ramit"
... },
... {
... "StudentId" : 7,
... "StudentName" : "Adam"
... },
... {
... "StudentId" : 8,
... "StudentName" : "Larry"
... }
... ]
... }
...
... );
{ "acknowledged" : true, "insertedId" : 200 }以下是在find()方法的帮助下显示集合中所有文档的查询
> db.deleteDocumentsDemo.find().pretty();
这将产生以下输出
{
"_id" : 100,
"StudentsDetails" : [
{
"StudentId" : 1,
"StudentName" : "John"
},
{
"StudentId" : 2,
"StudentName" : "Carol"
},
{
"StudentId" : 3,
"StudentName" : "Sam"
},
{
"StudentId" : 4,
"StudentName" : "Mike"
}
]
}
{
"_id" : 200,
"StudentsDetails" : [
{
"StudentId" : 5,
"StudentName" : "David"
},
{
"StudentId" : 6,
"StudentName" : "Ramit"
},
{
"StudentId" : 7,
"StudentName" : "Adam"
},
{
"StudentId" : 8,
"StudentName" : "Larry"
}
]
}以下是删除数组中文档的查询
> db.deleteDocumentsDemo.update({},
... {$pull: {StudentsDetails: {StudentName: "David"}}},
... {multi: true});
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 1 })让我们检查文件是否被删除。以下是查询
> db.deleteDocumentsDemo.find().pretty();
这将产生以下输出
{
"_id" : 100,
"StudentsDetails" : [
{
"StudentId" : 1,
"StudentName" : "John"
},
{
"StudentId" : 2,
"StudentName" : "Carol"
},
{
"StudentId" : 3,
"StudentName" : "Sam"
},
{
"StudentId" : 4,
"StudentName" : "Mike"
}
]
}
{
"_id" : 200,
"StudentsDetails" : [
{
"StudentId" : 6,
"StudentName" : "Ramit"
},
{
"StudentId" : 7,
"StudentName" : "Adam"
},
{
"StudentId" : 8,
"StudentName" : "Larry"
}
]
}查看上面的示例输出，已删除值为5的“StudentId”，即StudentName“David”。