MongoDB管理与开发精要《红丸出品》5.2 游标

游标

象大多数数据库产品一样，MongoDB也是用游标来循环处理每一条结果数据，具体语法如下：

> for( var c = db.t3.find(); c.hasNext(); ) {

...    printjson( c.next());

... }

{ "_id" : ObjectId("4fb8e4838b2cb86417c9423a"), "age" : 1 }

{ "_id" : ObjectId("4fb8e4878b2cb86417c9423b"), "age" : 2 }

{ "_id" : ObjectId("4fb8e4898b2cb86417c9423c"), "age" : 3 }

{ "_id" : ObjectId("4fb8e48c8b2cb86417c9423d"), "age" : 4 }

{ "_id" : ObjectId("4fb8e48e8b2cb86417c9423e"), "age" : 5 }

 

MongoDB还有另一种方式来处理游标

> db.t3.find().forEach( function(u) { printjson(u); } );

{ "_id" : ObjectId("4fb8e4838b2cb86417c9423a"), "age" : 1 }

{ "_id" : ObjectId("4fb8e4878b2cb86417c9423b"), "age" : 2 }

{ "_id" : ObjectId("4fb8e4898b2cb86417c9423c"), "age" : 3 }

{ "_id" : ObjectId("4fb8e48c8b2cb86417c9423d"), "age" : 4 }

{ "_id" : ObjectId("4fb8e48e8b2cb86417c9423e"), "age" : 5 }

>