MongoDB聚合运算符:$setUnion

MongoDB聚合运算符:$setUnion

文章目录

  • [MongoDB聚合运算符:setUnion](#MongoDB聚合运算符:setUnion)

$setUnion聚合运算符返回两个或多个数组的并集。

语法

js 复制代码
{ $setUnion: [ <expression1>, <expression2>, ... ] }

<expression>为可解析为数组的表达式。

使用

$setUnion对数组执行集合操作,将数组视为集合。如果数组包含重复元素,$setUnion会忽略重复元素,并且$setUnion也会忽略元素的顺序。

如果集合包含嵌套数组元素,$setUnion 不会进入嵌套数组,而对顶层对数组进行评估。

举例 结果
{ $setUnion: [ [ "a", "b", "a" ], [ "b", "a" ] ] } [ "b", "a" ]
{ $setUnion: [ [ "a", "b" ], [ [ "a", "b" ] ] ] } [ [ "a", "b" ], "b", "a" ]

举例

使用下面的脚本创建flowers集合:

js 复制代码
db.flowers.insertMany( [
   { "_id" : 1, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid" ] },
   { "_id" : 2, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "orchid", "rose", "orchid" ] },
   { "_id" : 3, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid", "jasmine" ] },
   { "_id" : 4, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "jasmine", "rose" ] },
   { "_id" : 5, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ ] },
   { "_id" : 6, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose" ], [ "orchid" ] ] },
   { "_id" : 7, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose", "orchid" ] ] },
   { "_id" : 8, "flowerFieldA" : [ ], "flowerFieldB" : [ ] },
   { "_id" : 9, "flowerFieldA" : [ ], "flowerFieldB" : [ "rose" ] }
] )

下面的操作使用$setUnion运算符返回在数组flowerFieldA或数组flowerFieldB中出现的元素的数组,就是两个数组的并集:

js 复制代码
db.flowers.aggregate(
   [
     { $project: { flowerFieldA:1, flowerFieldB: 1, allValues: { $setUnion: [ "$flowerFieldA", "$flowerFieldB" ] }, _id: 0 } }
   ]
)

操作返回下面的结果:

json 复制代码
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ "rose", "orchid" ], "allValues": [ "orchid", "rose" ] }
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ "orchid", "rose", "orchid" ], "allValues": [ "orchid", "rose" ] }
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ "rose", "orchid", "jasmine" ], "allValues": [ "orchid", "rose", "jasmine" ] }
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ "jasmine", "rose" ], "allValues": [ "orchid", "rose", "jasmine" ] }
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ ], "allValues": [ "orchid", "rose" ] }
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ [ "rose" ], [ "orchid" ] ], "allValues": [ "orchid", "rose", [ "rose" ], [ "orchid" ] ] }
{ "flowerFieldA": [ "rose", "orchid" ], "flowerFieldB": [ [ "rose", "orchid" ] ], "allValues": [ "orchid", "rose", [ "rose", "orchid" ] ] }
{ "flowerFieldA": [ ], "flowerFieldB": [ ], "allValues": [ ] }
{ "flowerFieldA": [ ], "flowerFieldB": [ "rose" ], "allValues": [ "rose" ] }
相关推荐
摩羯座-1856903059416 小时前
爬坑 10 年!京东店铺全量商品接口实战开发:从分页优化、SKU 关联到数据完整性闭环
linux·网络·数据库·windows·爬虫·python
编程充电站pro17 小时前
SQL 面试高频:INNER JOIN vs LEFT JOIN 怎么考?
数据库·sql
这周也會开心17 小时前
SQL-窗口函数做题总结
数据库·sql
间彧17 小时前
TiDB详解与Spring Boot实战指南
数据库
极限实验室17 小时前
Easysearch 字段'隐身'之谜:source_reuse 与 ignore_above 的陷阱解析
数据库·redis
2301_7720935617 小时前
tuchuang_后端_前端_注册登录
数据库·后端·网络协议·mysql·wireshark
武子康17 小时前
Java-141 深入浅出 MySQL Spring事务失效的常见场景与解决方案详解(3)
java·数据库·mysql·spring·性能优化·系统架构·事务
间彧17 小时前
脏读、不可重复读、幻读详解与对比
数据库
间彧18 小时前
数据库事务隔离级别详解
数据库
fwerfv34534518 小时前
使用PyTorch构建你的第一个神经网络
jvm·数据库·python