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db.command.aggregate.setUnion

1. 操作符描述#

功能:输入两个集合,输出两个集合的并集。

声明:`db.command.aggregate.setUnion([expression1, expression2])

2. 操作符参数#

字段类型必填说明
-<Array>Expression聚合表达式数组

3. 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 setUnion,输出两个集合的并集:

// 云函数环境下示例代码const tcb = require('@cloudbase/node-sdk')const app = tcb.init({  env: 'xxx'})
const db = app.database()const $ = db.command.aggregateconst _ = db.command
exports.main = async (event, context) => {  const res = await db    .collection('test')    .aggregate()    .project({      AB: $.setUnion(['$A', '$B'])    })    .end()  console.log(res.data)}

输出如下:

{ "_id": 1, "AB": [ 1, 2 ] }{ "_id": 2, "AB": [ 1, 2 ] }{ "_id": 3, "AB": [ 1, 2, 3 ] }{ "_id": 4, "AB": [ 1, 2, 3 ] }{ "_id": 5, "AB": [ 1, 2 ] }{ "_id": 6, "AB": [ 1, 2, {}, [] ] }{ "_id": 7, "AB": [ ] }{ "_id": 8, "AB": [ 1 ] }