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db.command.aggregate.add

1. 操作符描述#

功能:将数字相加或将数字加在日期上。如果数组中的其中一个值是日期,那么其他值将被视为毫秒数加在该日期上。

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

2. 操作符参数#

字段类型必填说明
-<Array>Expression字符串表达式可以是形如 $ + 指定字段,也可以是普通字符串。只要能够被解析成字符串即可。

3. 示例代码#

假设集合 staff 有如下记录:

{ _id: 1, department: "x", sales: 5, engineer: 10, lastUpdate: ISODate("2019-05-01T00:00:00Z") }{ _id: 2, department: "y", sales: 10, engineer: 20, lastUpdate: ISODate("2019-05-01T02:00:00Z") }{ _id: 3, department: "z", sales: 20, engineer: 5, lastUpdate: ISODate("2019-05-02T03:00:00Z") }

数字求和#

可以用如下方式求得各个记录人数总数:

// 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.aggregate
exports.main = async (event, context) => {  const res = await db    .collection('staff')    .aggregate()    .project({      department: 1,      total: $.add(['$sales', '$engineer'])    })    .end()  console.log(res.data) // 打印聚合结果}

返回结果如下:

{ _id: 1, department: "x", total: 15 }{ _id: 2, department: "y", total: 30 }{ _id: 3, department: "z", total: 25 }

增加日期值#

如下操作可以获取各个记录的 lastUpdate 加一个小时之后的值:

// 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.aggregate
exports.main = async (event, context) => {  const res = await db    .collection('staff')    .aggregate()    .project({      department: 1,      lastUpdate: $.add(['$lastUpdate', 60 * 60 * 1000])    })    .end()  console.log(res.data) // 打印聚合结果}

返回结果如下:

{ _id: 1, department: "x", lastUpdate: ISODate("2019-05-01T01:00:00Z") }{ _id: 2, department: "y", lastUpdate: ISODate("2019-05-01T03:00:00Z") }{ _id: 3, department: "z", lastUpdate: ISODate("2019-05-02T04:00:00Z") }