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Legal Studies在使用 limit 限制條件的同時獲取 MongoDB 中文件的總數？
你可以使用 $facet 運算子來實現此目的。為了理解該概念，讓我們先建立一個包含文件的集合。建立包含文件的集合的查詢如下 −
> 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() 方法的幫助下，顯示集合中的所有文件。查詢如下 −
> db.totalDocumentDemo.find().pretty();
輸出
{
"_id" : ObjectId("5c76e6701e9c5dd6f1f78274"),
"InstructorId" : 100,
"InstructorName" : "Larry",
"InstructorFavouriteSubject" : [
"Java",
"MongoDB",
"Python"
]
}
{
"_id" : ObjectId("5c76e69c1e9c5dd6f1f78275"),
"InstructorId" : 200,
"InstructorName" : "Sam",
"InstructorFavouriteSubject" : [
"SQL Server",
"C#",
"Javascript"
]
}以下是獲取集合中文件總數的查詢 −
> db.totalDocumentDemo.aggregate([
... {
... $facet:{
... Alldata:[{$match:{}}],
... totalDocument: [{ $count: 'totalDocument' }]
... }
... }
... ]).pretty();以下是顯示文件數量的輸出 −
輸出
{
"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
}
]
}
更新於: 30-Jul-2019
657 次瀏覽
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