是的,使用$in更快。让我们看一个示例并创建包含文档的集合-
> db.demo653.insertOne({subject:"MySQL"}); { "acknowledged" : true, "insertedId" : ObjectId("5ea04b274deddd72997713c0") } > db.demo653.insertOne({subject:"MongoDB"}); { "acknowledged" : true, "insertedId" : ObjectId("5ea04b304deddd72997713c1") } > db.demo653.insertOne({subject:"Java"}); { "acknowledged" : true, "insertedId" : ObjectId("5ea04b354deddd72997713c2") } > db.demo653.insertOne({subject:"C"}); { "acknowledged" : true, "insertedId" : ObjectId("5ea04b384deddd72997713c3") } > db.demo653.insertOne({subject:"C++"}); { "acknowledged" : true, "insertedId" : ObjectId("5ea04b3b4deddd72997713c4") }
在find()
方法的帮助下显示集合中的所有文档-
> db.demo653.find();
这将产生以下输出-
{ "_id" : ObjectId("5ea04b274deddd72997713c0"), "subject" : "MySQL" } { "_id" : ObjectId("5ea04b304deddd72997713c1"), "subject" : "MongoDB" } { "_id" : ObjectId("5ea04b354deddd72997713c2"), "subject" : "Java" } { "_id" : ObjectId("5ea04b384deddd72997713c3"), "subject" : "C" } { "_id" : ObjectId("5ea04b3b4deddd72997713c4"), "subject" : "C++" }
以下是使用$in和比多个单次搜索更快的查询的查询-
> db.demo653.find({subject:{$in:["MySQL","C++","C"]}});
这将产生以下输出-
{ "_id" : ObjectId("5ea04b274deddd72997713c0"), "subject" : "MySQL" } { "_id" : ObjectId("5ea04b384deddd72997713c3"), "subject" : "C" } { "_id" : ObjectId("5ea04b3b4deddd72997713c4"), "subject" : "C++" }