您的位置：首页 > 数据库 > Mongodb

【mongoDB实战】聚合管道--$unwind

2017-06-27 11:48 369 查看

$unwind：将文档中的某一个数组类型字段拆分成多条，每条包含数组中的一个值。

在做项目的时候碰上了这样的需求:

实例讲解:

{
"_id" : ObjectId("5951c5de567ebff0d5011fba"),
"name" : "陈晓婵",
"address" : "北京朝阳区",
"weekday" : [
1,
2,
3,
4,
5
]
}

对weekday进行拆分:

db.getCollection('chenxiaochantest').aggregate(
[
{
$unwind:"$weekday"
}
]
)

拆分结果:

/* 1 */
{
"_id" : ObjectId("5951c5de567ebff0d5011fba"),
"name" : "陈晓婵",
"address" : "北京朝阳区",
"weekday" : 1
}

/* 2 */
{
"_id" : ObjectId("5951c5de567ebff0d5011fba"),
"name" : "陈晓婵",
"address" : "北京朝阳区",
"weekday" : 2
}

/* 3 */
{
"_id" : ObjectId("5951c5de567ebff0d5011fba"),
"name" : "陈晓婵",
"address" : "北京朝阳区",
"weekday" : 3
}

/* 4 */
{
"_id" : ObjectId("5951c5de567ebff0d5011fba"),
"name" : "陈晓婵",
"address" : "北京朝阳区",
"weekday" : 4
}

/* 5 */
{
"_id" : ObjectId("5951c5de567ebff0d5011fba"),
"name" : "陈晓婵",
"address" : "北京朝阳区",
"weekday" : 5
}

使用$unwind可以将weekday中的每个数据都被分解成一个文档,并且除了weekday的值不同外,其他的值都是相同的.

实例讲解:

{
"_id" : ObjectId("5951ca15567ebff0d5011fbb"),
"name" : "陈晓婵",
"address" : "北京朝阳",
"lunch" : [
{
"food" : "baozi",
"fruit" : "taozi"
},
{
"food" : "miaotiao",
"fruit" : "xigua"
}
]
}

对lunch进行拆分:

db.getCollection('chenxiaochantest2').aggregate(
[
{
$unwind:"$lunch"
}
]
)

拆分结果:

/* 1 */
{
"_id" : ObjectId("5951ca15567ebff0d5011fbb"),
"name" : "陈晓婵",
"address" : "北京朝阳",
"lunch" : {
"food" : "baozi",
"fruit" : "taozi"
}
}

/* 2 */
{
"_id" : ObjectId("5951ca15567ebff0d5011fbb"),
"name" : "陈晓婵",
"address" : "北京朝阳",
"lunch" : {
"food" : "miaotiao",
"fruit" : "xigua"
}
}

使用$unwind可以将lunch中的每个数据都被分解成一个文档,并且除了lunch的值不同外,其他的值都是相同的.

内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理

标签： mongodb unwind

相关文章推荐

新的分享

章节导航