MongoDB查询以从集合中查找特定的城市记录
为此，请使用find()并获取特定记录。让我们创建一个包含文档的集合-
> db.demo30.insertOne({"City":"New York"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e174ceccfb11e5c34d898bd")
}
> db.demo30.insertOne({"City":"Los Angeles"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e174d0ecfb11e5c34d898be")
}
> db.demo30.insertOne({"City":"Chicago"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e174d18cfb11e5c34d898bf")
}
> db.demo30.insertOne({"City":"Los Angeles"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e174d1dcfb11e5c34d898c0")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo30.find();
这将产生以下输出-
{ "_id" : ObjectId("5e174ceccfb11e5c34d898bd"), "City" : "New York" }
{ "_id" : ObjectId("5e174d0ecfb11e5c34d898be"), "City" : "Los Angeles" }
{ "_id" : ObjectId("5e174d18cfb11e5c34d898bf"), "City" : "Chicago" }
{ "_id" : ObjectId("5e174d1dcfb11e5c34d898c0"), "City" : "Los Angeles" }这是查找特定城市的查询-
> db.demo30.find({"City":"Chicago"});这将产生以下输出-
{ "_id" : ObjectId("5e174d18cfb11e5c34d898bf"), "City" : "Chicago" }