Docs 菜单
Docs 主页
/
数据库手册
/
聚合操作
/
参考
/
操作符

$setUnion (aggregation)

在此页面上

定义

$setUnion

Takes two or more arrays and returns an array containing the elements that appear in any input array.

$setUnion 采用以下语法：

{ $setUnion: [ <expression1>, <expression2>, ... ] }

参数可以是任何有效的表达式，只要它们都解析为一个数组即可。有关表达式的更多信息，请参阅表达式运算符。

行为

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

$setUnion 会过滤掉结果中的重复项，输出仅包含唯一条目的数组。输出数组中元素的顺序未指定。

如果集合包含嵌套数组元素，$setUnion不会下降进入嵌套数组，而是在顶层计算数组。

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

注意

Starting in MongoDB 5.2, the sort order for $setUnion is undefined. To sort an array, refer to $sortArray.

例子

考虑包含以下文档的 flowers 集合：

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" ] }
] )

The following operation uses the $setUnion operator to return an array of elements found in the flowerFieldA array or the flowerFieldB array or both:

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

操作返回以下结果：

{ "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" ] }

后退

$setIsSubset

来年

$shift

在此页面上