【发布时间】：2020-09-16 10:04:27
【问题描述】：
我有一个 MongoDB 数据库，其中每个条目都有一个“comment”字段。我正在使用 MongoDB Compass 连接到它，并尝试查找“comment”字段的所有唯一值。我在 Compass 的“Aggregations”选项卡中尝试了以下代码（见下图），但没有得到任何结果：
{$group: {
_id: null,
unique_comments: {
$addToSet: comment
}
}
JSON 格式的数据示例如下：
{"name":"Hannah Maxwell","date":"2020-01-07T20:16:13.931629-08:00","comment":"Maybe I like camping","location":{"latitude":43.81710433959961,"longitude":-79.42430114746094,"country":"CA","region":"ON"},"likes":1,"responses":24}
{"name":"Jordan Rodriguez","date":"2019-04-28T20:16:13.931629-07:00","comment":"I hate skiing","location":{"latitude":43.41518783569336,"longitude":-80.51475524902344,"country":"CA","region":"ON"},"likes":5,"responses":1}
{"name":"Bodhi Mckenzie","date":"2019-07-09T20:16:13.931629-07:00","comment":"I think I might like skiing","location":{"latitude":43.65549087524414,"longitude":-79.38555908203125,"country":"CA","region":"ON"},"likes":65,"responses":5}
【问题讨论】：
-
你试过了吗：
$addToSet: "$comment"？ -
是的，Micki，我刚刚尝试过，但它不起作用。 “预览”仍然是空的。
标签： json mongodb field mongodb-compass unique-values