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Legal Studies在使用 limit 限制条件的同时获取 MongoDB 中文档的总数？
你可以使用 $facet 运算符来实现此目的。为了理解该概念，让我们先创建一个包含文档的集合。创建包含文档的集合的查询如下 −
> db.totalDocumentDemo.insertOne({"InstructorId":100,"InstructorName":"Larry","InstructorFav
ouriteSubject":["Java","MongoDB","Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c76e6701e9c5dd6f1f78274")
}
> db.totalDocumentDemo.insertOne({"InstructorId":200,"InstructorName":"Sam","InstructorFav
ouriteSubject":["SQL Server","C#","Javascript"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c76e69c1e9c5dd6f1f78275")
}在 find() 方法的帮助下，显示集合中的所有文档。查询如下 −
> db.totalDocumentDemo.find().pretty();
输出
{
"_id" : ObjectId("5c76e6701e9c5dd6f1f78274"),
"InstructorId" : 100,
"InstructorName" : "Larry",
"InstructorFavouriteSubject" : [
"Java",
"MongoDB",
"Python"
]
}
{
"_id" : ObjectId("5c76e69c1e9c5dd6f1f78275"),
"InstructorId" : 200,
"InstructorName" : "Sam",
"InstructorFavouriteSubject" : [
"SQL Server",
"C#",
"Javascript"
]
}以下是获取集合中文档总数的查询 −
> db.totalDocumentDemo.aggregate([
... {
... $facet:{
... Alldata:[{$match:{}}],
... totalDocument: [{ $count: 'totalDocument' }]
... }
... }
... ]).pretty();以下是显示文档数量的输出 −
输出
{
"Alldata" : [
{
"_id" : ObjectId("5c76e6701e9c5dd6f1f78274"),
"InstructorId" : 100,
"InstructorName" : "Larry",
"InstructorFavouriteSubject" : [
"Java",
"MongoDB",
"Python"
]
},
{
"_id" : ObjectId("5c76e69c1e9c5dd6f1f78275"),
"InstructorId" : 200,
"InstructorName" : "Sam",
"InstructorFavouriteSubject" : [
"SQL Server",
"C#",
"Javascript"
]
}
],
"totalDocument" : [
{
"totalDocument" : 2
}
]
}
更新于: 30-Jul-2019
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