db.command.aggregate.setUnion
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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])
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2. 操作符参数字段 | 类型 | 必填 | 说明 |
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- | <Array>Expression | 是 | 聚合表达式数组 |
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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 ] }