从嵌套在MongoDB中另一个数组中的数组中删除特定记录？
要删除特定记录，请使用$pull运算符。首先让我们创建一个包含文档的集合-
> dbdeletingSpecificRecordDemoinsertOne(
{
"StudentDetails": [
{
"StudentName": "John",
"StudentSubjectDetails": [
{
"Subject": "MongoDB",
"Marks":45
},
{
"Subject": "MySQL",
"Marks":67
}
]
}
]
}
);
{
"acknowledged" : true,
"insertedId" : ObjectId("5cf2210ab64a577be5a2bc06")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> dbdeletingSpecificRecordDemofind()pretty();
这将产生以下文件-
{
"_id" : ObjectId("5cf2210ab64a577be5a2bc06"),
"StudentDetails" : [
{
"StudentName" : "John",
"StudentSubjectDetails" : [
{
"Subject" : "MongoDB",
"Marks" : 45
},
{
"Subject" : "MySQL",
"Marks" : 67
}
]
}
]
}这是从嵌套在另一个数组中的数组中删除特定记录的查询-
> dbdeletingSpecificRecordDemoupdate({"_id": ObjectId("5cf2210ab64a577be5a2bc06"), "StudentDetailsStudentName" : "John"},
{
"$pull": {"StudentDetails$StudentSubjectDetails" : { "Marks":45 }}
}, multi=true
);
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })让我们再次检查文档-
> dbdeletingSpecificRecordDemofind()pretty();
这将产生以下文件-
{
"_id" : ObjectId("5cf2210ab64a577be5a2bc06"),
"StudentDetails" : [
{
"StudentName" : "John",
"StudentSubjectDetails" : [
{
"Subject" : "MySQL",
"Marks" : 67
}
]
}
]
}