Mongodb aggregate commonly used statements

 

Comparison of commonly used aggregation statements and sql statements in Mongodb:

       

1. $match is equivalent to where
2. $group is equivalent to group by
3. $match is equivalent to having
4. $project is equivalent to select
5. $sort is equivalent to order by
6. $limit is equivalent to limit
7. $sum is equivalent to sum()
8. $count() is equivalent to count()
9. Join is equivalent to $lookup
10. The match before the group is to query the source data, and the match after the group is to filter the data after the group
11. $in: Query multiple data, that is, a field element is in a list
12. $nin: Query multiple data, that is, a certain field element is not in the same list
13. $ne: not equal
14. $gt/$gte: greater than/greater than or equal to
15. $lt/$lte: less than/less than or equal to
16. $set: add a new field, or update a field

Mongodb aggregate query, examples:

      db.table.aggregate([{$match:{“status”:1}},

           {$group:{_id:”$cust_id”,total:{$sum:”$price”}}}])

    解析：sql: select cust_id,sum(price) as total from table where status=1 group by cust_id