如何在 MongoDB 中查找不包含特定字段的项目?
mongodbdatabasebig data analytics更新于 2026/1/24 3:37:17
要查找不包含特定字段的项目，请使用 $exists 运算符。语法如下:−
> db.yourCollectionName.find({"yourItemName":{$exists:false}}).pretty();
为了理解语法，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 −
> db.findDocumentDoNotHaveCertainFields.insertOne({"UserId":101,"UserName":"John","UserAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8a95fb6cea1f28b7aa07fb")
}
> db.findDocumentDoNotHaveCertainFields.insertOne({"UserName":"David","UserAge":22,"UserFavouriteSubject":["C","Java"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8a96116cea1f28b7aa07fc")
}
> db.findDocumentDoNotHaveCertainFields.insertOne({"UserName":"Bob","UserAge":24,"UserFavouriteSubject":["MongoDB","MySQL"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8a96306cea1f28b7aa07fd")
}
使用 find() 方法显示集合中的所有文档。查询如下 −
> db.findDocumentDoNotHaveCertainFields.find().pretty();
以下是输出 −
{
"_id" : ObjectId("5c8a95fb6cea1f28b7aa07fb"),
"UserId" : 101,
"UserName" : "John",
"UserAge" : 21
}
{
"_id" : ObjectId("5c8a96116cea1f28b7aa07fc"),
"UserName" : "David",
"UserAge" : 22,
"UserFavouriteSubject" : [
"C",
"Java"
]
}
{
"_id" : ObjectId("5c8a96306cea1f28b7aa07fd"),
"UserName" : "Bob",
"UserAge" : 24,
"UserFavouriteSubject" : [
"MongoDB",
"MySQL"
]
}
以下查询用于查找不包含特定字段(即 UserFavouriteSubject)的项目 −
> db.findDocumentDoNotHaveCertainFields.find({"UserFavouriteSubject":{$exists:false}}).pretty();
以下是输出 −
{
"_id" : ObjectId("5c8a95fb6cea1f28b7aa07fb"),
"UserId" : 101,
"UserName" : "John",
"UserAge" : 21
}
