如何在MongoDB查询中从字段中修剪空间？
要从字段中修剪空间，请在MongoDB中使用$trim。让我们创建一个包含文档的集合-
> db.demo217.insertOne({"FullName":" Chris Brown"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3e5d1e03d395bdc213470f")
}
> db.demo217.insertOne({"FullName":" David Miller"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3e5d2503d395bdc2134710")
}
> db.demo217.insertOne({"FullName":" John Doe"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3e5d2b03d395bdc2134711")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo217.find();
这将产生以下输出-
{ "_id" : ObjectId("5e3e5d1e03d395bdc213470f"), "FullName" : " Chris Brown" }
{ "_id" : ObjectId("5e3e5d2503d395bdc2134710"), "FullName" : " David Miller" }
{ "_id" : ObjectId("5e3e5d2b03d395bdc2134711"), "FullName" : " John Doe" }以下是从MongoDB中的字段中修剪空间的查询-
> db.demo217.aggregate([
... { $project: { Name: { $trim: { input: "$FullName" } } } }
... ])这将产生以下输出-
{ "_id" : ObjectId("5e3e5d1e03d395bdc213470f"), "Name" : "Chris Brown" }
{ "_id" : ObjectId("5e3e5d2503d395bdc2134710"), "Name" : "David Miller" }
{ "_id" : ObjectId("5e3e5d2b03d395bdc2134711"), "Name" : "John Doe" }