等效语法如下。
db.yourCollectionName.find({}, {_id: 1, "column1": 1, "column2": 1}).pretty();
为了理解上述语法,让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.equivalentForSelectColumn1Column2Demo.insertOne({"CustomerName":"John","CustomerAge":26,"CustomerCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5c92c6205259fcd19549980a") } > db.equivalentForSelectColumn1Column2Demo.insertOne({"CustomerName":"David","CustomerAge":22,"CustomerCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5c92c6305259fcd19549980b") } > db.equivalentForSelectColumn1Column2Demo.insertOne({"CustomerName":"Chris","CustomerAge":24,"CustomerCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5c92c6415259fcd19549980c") }
在find()
method的帮助下显示集合中的所有文档。查询如下-
> db.equivalentForSelectColumn1Column2Demo.find().pretty();
以下是输出-
{ "_id" : ObjectId("5c92c6205259fcd19549980a"), "CustomerName" : "John", "CustomerAge" : 26, "CustomerCountryName" : "US" } { "_id" : ObjectId("5c92c6305259fcd19549980b"), "CustomerName" : "David", "CustomerAge" : 22, "CustomerCountryName" : "AUS" } { "_id" : ObjectId("5c92c6415259fcd19549980c"), "CustomerName" : "Chris", "CustomerAge" : 24, "CustomerCountryName" : "UK" }
这是MongoDB数据库中tbl的select column1,column2的等效语法-
> db.equivalentForSelectColumn1Column2Demo.find({}, {"CustomerName": 1, "CustomerAge": 1}).pretty();
以下是输出-
{ "_id" : ObjectId("5c92c6205259fcd19549980a"), "CustomerName" : "John", "CustomerAge" : 26 } { "_id" : ObjectId("5c92c6305259fcd19549980b"), "CustomerName" : "David", "CustomerAge" : 22 } { "_id" : ObjectId("5c92c6415259fcd19549980c"), "CustomerName" : "Chris", "CustomerAge" : 24 }
如果您不想包含_id,请使用以下查询-
> db.equivalentForSelectColumn1Column2Demo.find({}, {_id: 0, "CustomerName": 1, "CustomerAge": 1}).pretty();
以下是输出-
{ "CustomerName" : "John", "CustomerAge" : 26 } { "CustomerName" : "David", "CustomerAge" : 22 } { "CustomerName" : "Chris", "CustomerAge" : 24 }