document
- https://www.mongodb.com/docs/manual/aggregation/
- Operators for aggregation queries https://www.mongodb.com/docs/manual/reference/operator/aggregation/
Classification of Aggregate Query Operators
- arithmetic expression operator
- array expression operator
- boolean expression operator
- comparison expression operator
- conditional expression operator
- …
Common Mongo aggregation operations are compared with mysql queries
| SQL | Aggregate |
|---|---|
| where | $match |
| group by | $group |
| having | $match |
| select | $project |
| order by | $project |
| limit | $limit |
| sum() | $sum |
| count() | $sum |
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