布尔值到字符串的聚合更改值

Question

有一个包含记录的集合，需要将列的布尔值转换为字符串：

[
  {
    _id: "bmasndvhjbcw",
    name: "lucas",
    occupation: "scientist",
    passed_phd: true,
    age: 55,
    location: "texas",

  },
  {
    _id: "bmasndvhjbcx",
    name: "mark",
    occupation: "scientist",
    age: 45,
    passed_phd: true,
    location: "texas",

  },
  {
    _id: "bmasndvhjbca",
    name: "stuart",
    occupation: "lab assistant",
    age: 25,
    passed_phd: false,
    location: "texas",

  },
  {
    _id: "bmasndvhjbcq",
    name: "cooper",
    occupation: "physicist",
    age: 69,
    passed_phd: false,
    location: "texas"
  }
]

如何将记录的布尔值更改为字符串。

passed_phd 中具有 true(boolean) 的值应转换为 "yes"(string)

passed_phd 中包含 false(boolean) 的值应转换为“no”(string)

[
  {
    _id: "bmasndvhjbcw",
    name: "lucas",
    occupation: "scientist",
    passed_phd: "yes",
    age: 55,
    location: "texas",

  },
  {
    _id: "bmasndvhjbcx",
    name: "mark",
    occupation: "scientist",
    age: 45,
    passed_phd: "yes",
    location: "texas",

  },
  {
    _id: "bmasndvhjbca",
    name: "stuart",
    occupation: "lab assistant",
    age: 25,
    passed_phd: "no",
    location: "texas",

  },
  {
    _id: "bmasndvhjbcq",
    name: "cooper",
    occupation: "physicist",
    age: 69,
    passed_phd: "no",
    location: "texas"
  }
]

mongodb 4.0 版 .

Answer 1

$cond 聚合管道运算符可以做到这一点。

从 MongoDB 4.2 开始，这些可用于更新或聚合管道，例如：

db.collection.aggregate([
    {$set:{
            passed_phd:{
                        $cond:{
                               if:"$passed_phd",
                               then:"yes",
                               else:"no"
                              }
                        }
   }}
])