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法律研究选择既不存在、为空或为 false 的 MongoDB 中的字段中的记录?
你可以使用 $in 运算符来完成此操作。首先让我们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所示 -
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":1,"StudentName":"Larry"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9010215705caea966c557f")
}
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":2,"StudentName":"Mike","hasAgeGreaterThanOrEqualTo18":true});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c90106a5705caea966c5580")
}
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":3,"StudentName":"Carol","hasAgeGreaterThanOrEqualTo18":false});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9010795705caea966c5581")
}
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":4,"StudentName":"Sam","hasAgeGreaterThanOrEqualTo18":null});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9010865705caea966c5582")
}
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":5,"StudentName":"David","hasAgeGreaterThanOrEqualTo18":false});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9010945705caea966c5583")
}
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":6,"StudentName":"Chris","hasAgeGreaterThanOrEqualTo18":null});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9010a45705caea966c5584")
}
> db.selectMongoDBDocumentsWithSomeCondition.insertOne({"StudentId":7,"StudentName":"Robert","hasAgeGreaterThanOrEqualTo18":true});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9010b05705caea966c5585")
}使用 find() 方法显示集合中的所有文档。查询如下所示 -
> db.selectMongoDBDocumentsWithSomeCondition.find().pretty();
以下为输出 -
{
"_id" : ObjectId("5c9010215705caea966c557f"),
"StudentId" : 1,
"StudentName" : "Larry"
}
{
"_id" : ObjectId("5c90106a5705caea966c5580"),
"StudentId" : 2,
"StudentName" : "Mike",
"hasAgeGreaterThanOrEqualTo18" : true
}
{
"_id" : ObjectId("5c9010795705caea966c5581"),
"StudentId" : 3,
"StudentName" : "Carol",
"hasAgeGreaterThanOrEqualTo18" : false
}
{
"_id" : ObjectId("5c9010865705caea966c5582"),
"StudentId" : 4,
"StudentName" : "Sam",
"hasAgeGreaterThanOrEqualTo18" : null
}
{
"_id" : ObjectId("5c9010945705caea966c5583"),
"StudentId" : 5,
"StudentName" : "David",
"hasAgeGreaterThanOrEqualTo18" : false
}
{
"_id" : ObjectId("5c9010a45705caea966c5584"),
"StudentId" : 6,
"StudentName" : "Chris",
"hasAgeGreaterThanOrEqualTo18" : null
}
{
"_id" : ObjectId("5c9010b05705caea966c5585"),
"StudentId" : 7,
"StudentName" : "Robert",
"hasAgeGreaterThanOrEqualTo18" : true
}以下是如何选择字段不存在、为空或为 false 的 MongoDB 文档的查询 -
> db.selectMongoDBDocumentsWithSomeCondition.find({ "hasAgeGreaterThanOrEqualTo18": {$in: [false,null]}}).pretty();以下为输出 -
{
"_id" : ObjectId("5c9010215705caea966c557f"),
"StudentId" : 1,
"StudentName" : "Larry"
}
{
"_id" : ObjectId("5c9010795705caea966c5581"),
"StudentId" : 3,
"StudentName" : "Carol",
"hasAgeGreaterThanOrEqualTo18" : false
}
{
"_id" : ObjectId("5c9010865705caea966c5582"),
"StudentId" : 4,
"StudentName" : "Sam",
"hasAgeGreaterThanOrEqualTo18" : null
}
{
"_id" : ObjectId("5c9010945705caea966c5583"),
"StudentId" : 5,
"StudentName" : "David",
"hasAgeGreaterThanOrEqualTo18" : false
}
{
"_id" : ObjectId("5c9010a45705caea966c5584"),
"StudentId" : 6,
"StudentName" : "Chris",
"hasAgeGreaterThanOrEqualTo18" : null
}
更新于: 30-7-2019
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