MongoDB 聚合框架进阶使用中$unwind要学习什么

查找个人最好成绩科目； { name: '张三', score: [{subject: '语文', score: 84}, {subject: '数学', score: 90}, {subject: '外语', score: 69}]

} db.students.aggregate([{$unwind: 'score'}]) {name: '张三', score: {subject: '语文', score: 84}} {name: '张三', score: {subject: '数学', score: 90}} {name: '张三', score: {subject: '外语', score: 69}} db.students.aggregate([ {$unwind: '$score'}, {$sort: {name:1, "score.score": -1}} ]} {name: '张三', score: {subject: '数学', score: 90}} {name: '张三', score: {subject: '语文', score: 84}} {name: '张三', score: {subject: '外语', score: 69}}