NodeJs操作MongoDB之多表查询($lookup)与常见问题 一,方法介绍 aggregate()方法来对数据进行聚合操作。aggregate()方法的语法如下1 aggregate(operators,[options],callback)operators参数是如表1所示的聚合运算符的数组，它允许你定义对数据执行什么汇总操作。options参数允许你设置readPreference属性，它定义了从哪里读取数据。callback参数是接受err和res $lookup:可以做多表查询1 { 2 $lookup://$lookup是如果涉...
db.ClassMembers.insertMany([ { "ClassID":"CL0001", "StudentID":"S000001", "DateFrom":"2015-09-01" }, { "ClassID":"CL0002", "StudentID":"S000002", "DateFrom":"2015-09-01" }]);db.Scores.insertMany([{ "StudentID":"S000001", "TestID":"T000001", "Scores":[{ "Course":"Chinese", "Score":80 },{ "Course":"Maths", "Score":...
相关数据存放在一起，针对性的查询可以消除join，性能比分散存储要高且方便 MongoDB中级---->关联多表查询 [日期：2011-08-19] 来源：Linux社区 作者：crazyjixiang [字体：]DBRef is a more formal specification for creating references between documents. DBRefs (generally) include a collection name as well as an object id. Most developers only use DBRefs if the collection can change from one document to the...