mongodb distinct count
As already pointed out by JohnnyHK, use db.collection.distinct if possible as it provides the chance of leveraging indexes. So in your case ...,Harder - Count with $project and $cond. Use project to create a 'hasCat' field. You will need to use $cond to do this: http://docs.mongodb.
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 mongodb distinct count 相關參考資料
Count distinct value in MongoDB? - Tutorialspoint
Use the concept of length to count distinct value. Following is the syntax −db.yourCollectionName.distinct(yourFieldName).length;Let us create ... https://www.tutorialspoint.com Count distinct values in mongoDB - Stack Overflow
As already pointed out by JohnnyHK, use db.collection.distinct if possible as it provides the chance of leveraging indexes. So in your case ... https://stackoverflow.com Counting distinct fields with $project and $match
Harder - Count with $project and $cond. Use project to create a 'hasCat' field. You will need to use $cond to do this: http://docs.mongodb. http://www.forwardadvance.com distinct() - db.collection.distinct() — MongoDB Manual
This page documents the mongo shell method, and does not refer to the MongoDB Node.js driver (or any other driver) method. For corresponding MongoDB driver ... https://docs.mongodb.com How to count all unique values In MONGODB? - Stack Overflow
db.getCollection('books').distinct('date'). if you want total number of unique values db.getCollection('books').distinct('date').length. https://stackoverflow.com mongodb count num of distinct values per fieldkey - Stack ...
If someone adds more documents with a new country I would like the query to return 9. Is there easier way then group and count? mongodb mongodb-query ... https://stackoverflow.com mongodb count num of distinct values per fieldkey - Stack Overflow
MongoDB has a distinct command which returns an array of distinct values for a field; you can check the length of the array for a count. There is ... https://stackoverflow.com MongoDB 去重(distinct)查询后求总数(count)_数据库_学习,你 ...
在使用MonoDB 做报表汇总经常的有去重统计总数的需求,在此总结一下实现方式: 1, 直接使用distinct 语句查询, 这种查询会将所有查询出来的数据 ... https://blog.csdn.net mongo中的高级查询之聚合操作(distinct,count,group) - 开源中国
Mongodb中自带的基本聚合函数有三种：count、distinct和group。下面我们分别来讲述一下这三个基本聚合函数。 （1）count. 作用：简单统计集合中 ... https://my.oschina.net “Count” and “Count Distinct” Queries in MongoDB | LichtenBytes
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