# AggregateCommand.setIntersection(value: Expression[]): Object
聚合操作符,输入两个集合,输出两个集合的交集。
# 参数
# value: Expression[]
[<expression1>, <expression2>]
# 返回值
# Object
# API 说明
使用形式如下:
setIntersection([<expression1>, <expression2>])
# 示例代码
假设集合 test
存在以下数据:
{ "_id": 1, "A": [ 1, 2 ], "B": [ 1, 2 ] }
{ "_id": 2, "A": [ 1, 2 ], "B": [ 2, 1, 2 ] }
{ "_id": 3, "A": [ 1, 2 ], "B": [ 1, 2, 3 ] }
{ "_id": 4, "A": [ 1, 2 ], "B": [ 3, 1 ] }
{ "_id": 5, "A": [ 1, 2 ], "B": [ ] }
{ "_id": 6, "A": [ 1, 2 ], "B": [ {}, [] ] }
{ "_id": 7, "A": [ ], "B": [ ] }
{ "_id": 8, "A": [ ], "B": [ 1 ] }
下面的代码使用 setIntersection
,输出两个集合的交集:
db.collection('test')
.aggregate()
.project({
commonToBoth: $.setIntersection(['$A', '$B'])
})
.end()
输出如下:
{ "_id": 1, "commonToBoth": [ 1, 2 ] }
{ "_id": 2, "commonToBoth": [ 1, 2 ] }
{ "_id": 3, "commonToBoth": [ 1, 2 ] }
{ "_id": 4, "commonToBoth": [ 1 ] }
{ "_id": 5, "commonToBoth": [ ] }
{ "_id": 6, "commonToBoth": [ ] }
{ "_id": 7, "commonToBoth": [ ] }
{ "_id": 8, "commonToBoth": [ ] }