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法律研究在 MongoDB 中查找数组大小大于 1 的文档的查询？
你可以使用 length 来查询数组大小大于 1 的文档
db.yourCollectionName.find({$where:"this.yourArrayDocumentName.length > 1"}).pretty();为了理解以上语法，让我们创建一个带有一些文档的集合。创建文档的集合查询如下
>db.arrayLengthGreaterThanOne.insertOne({"StudentName":"Larry","StudentTechnicalSubje
ct":["Java","C","C++"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6d6c4c0c3d5054b766a76a")
}
>db.arrayLengthGreaterThanOne.insertOne({"StudentName":"Maxwell","StudentTechnicalSu
bject":["MongoDB"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6d6c660c3d5054b766a76b")
}
>db.arrayLengthGreaterThanOne.insertOne({"StudentName":"Maxwell","StudentTechnicalSu
bject":["MySQL","SQL Server","PL/SQL"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6d6c800c3d5054b766a76c")
}在集合中显示所有文档，可以使用 find() 方法。查询如下
> db.arrayLengthGreaterThanOne.find().pretty();
输出如下
{
"_id" : ObjectId("5c6d6c4c0c3d5054b766a76a"),
"StudentName" : "Larry",
"StudentTechnicalSubject" : [
"Java",
"C",
"C++"
]
}
{
"_id" : ObjectId("5c6d6c660c3d5054b766a76b"),
"StudentName" : "Maxwell",
"StudentTechnicalSubject" : [
"MongoDB"
]
}
{
"_id" : ObjectId("5c6d6c800c3d5054b766a76c"),
"StudentName" : "Maxwell",
"StudentTechnicalSubject" : [
"MySQL",
"SQL Server",
"PL/SQL"
]
}以下是数组大小大于 1 的文档的查询。下面的查询将给出所有数组大小大于 1 的文档
> db.arrayLengthGreaterThanOne.find({$where:"this.StudentTechnicalSubject.length > 1"}).pretty();输出如下
{
"_id" : ObjectId("5c6d6c4c0c3d5054b766a76a"),
"StudentName" : "Larry",
"StudentTechnicalSubject" : [
"Java",
"C",
"C++"
]
}
{
"_id" : ObjectId("5c6d6c800c3d5054b766a76c"),
"StudentName" : "Maxwell",
"StudentTechnicalSubject" : [
"MySQL",
"SQL Server",
"PL/SQL"
]
}
更新于： 30-7 月-2019
623 次观看
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