从MongoDB中删除空字段
要删除空字段，请使用deleteMany()。首先让我们创建一个包含文档的集合-
> db.removeEmptyFieldsDemo.insertOne({"StudentName":""});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce92b9578f00858fb12e919")
}
> db.removeEmptyFieldsDemo.insertOne({"StudentName":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce92b9878f00858fb12e91a")
}
> db.removeEmptyFieldsDemo.insertOne({"StudentName":""});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce92b9c78f00858fb12e91b")
}
> db.removeEmptyFieldsDemo.insertOne({"StudentName":"Robert"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce92ba078f00858fb12e91c")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.removeEmptyFieldsDemo.find();
这将产生以下输出-
{ "_id" : ObjectId("5ce92b9578f00858fb12e919"), "StudentName" : "" }
{ "_id" : ObjectId("5ce92b9878f00858fb12e91a"), "StudentName" : "Chris" }
{ "_id" : ObjectId("5ce92b9c78f00858fb12e91b"), "StudentName" : "" }
{ "_id" : ObjectId("5ce92ba078f00858fb12e91c"), "StudentName" : "Robert" }以下是从MongoDB中删除空白字段的查询-
> db.removeEmptyFieldsDemo.updateMany({"StudentName": ""}, { $unset : {"StudentName" : 1 }});
{ "acknowledged" : true, "matchedCount" : 2, "modifiedCount" : 2 }让我们再次检查文档-
> db.removeEmptyFieldsDemo.find();
这将产生以下输出-
{ "_id" : ObjectId("5ce92b9578f00858fb12e919") }
{ "_id" : ObjectId("5ce92b9878f00858fb12e91a"), "StudentName" : "Chris" }
{ "_id" : ObjectId("5ce92b9c78f00858fb12e91b") }
{ "_id" : ObjectId("5ce92ba078f00858fb12e91c"), "StudentName" : "Robert" }