要为多个字段建立索引,请使用sureIndex()作为组合。使用sureIndex(),我们可以创建索引,甚至可以传递多个字段。让我们创建一个包含文档的集合-
> db.demo53.ensureIndex({"StudentFirstName":1,"StudentAge":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo53.ensureIndex({"StudentFirstName":1,"StudentCountryName":1}); { "createdCollectionAutomatically" : false, "numIndexesBefore" : 2, "numIndexesAfter" : 3, "ok" : 1 } >db.demo53.insertOne({"StudentFirstName":"Chris","StudentAge":21,"StudentCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5e271431cfb11e5c34d89911") } >db.demo53.insertOne({"StudentFirstName":"David","StudentAge":23,"StudentCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5e27143ccfb11e5c34d89912") } >db.demo53.insertOne({"StudentFirstName":"Mike","StudentAge":24,"StudentCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5e27144bcfb11e5c34d89913") }
在find()方法的帮助下显示集合中的所有文档-
> db.demo53.find();
这将产生以下输出-
{ "_id" : ObjectId("5e271431cfb11e5c34d89911"), "StudentFirstName" : "Chris", "StudentAge" : 21, "StudentCountryName" : "US" } { "_id" : ObjectId("5e27143ccfb11e5c34d89912"), "StudentFirstName" : "David", "StudentAge" : 23, "StudentCountryName" : "UK" } { "_id" : ObjectId("5e27144bcfb11e5c34d89913"), "StudentFirstName" : "Mike", "StudentAge" : 24, "StudentCountryName" : "AUS" }