• MongoDB for Time Series Data: Analyzing Time Series Data Using the Aggregation Framework and Hadoop 16 

• The Aggregation Framework 17 

• Webinar: Exploring the Aggregation Framework 18 

• Quick Reference Cards 19 

## 7.4 Aggregation Reference 

Aggregation Pipeline Quick Reference (page 469) Quick reference card for aggregation pipeline. 

http://docs.mongodb.org/manual/reference/operator/aggregation Aggregation pipeline operations have a collection of operators available to define and manipulate documents in pipeline stages. 

Aggregation Commands Comparison (page 474) A comparison of group , mapReduce and aggregate that ex- plores the strengths and limitations of each aggregation modality. 

SQL to Aggregation Mapping Chart (page 476) An overview common aggregation operations in SQL and Mon- goDB using the aggregation pipeline and operators in MongoDB and common SQL statements. 

Aggregation Commands (page 478) The reference for the data aggregation commands, which provide the interfaces to MongoDB’s aggregation capability. 

Variables in Aggregation Expressions (page 478) Use of variables in aggregation pipeline expressions. 

## 7.4.1 Aggregation Pipeline Quick Reference 

## Stages 

Pipeline stages appear in an array. Documents pass through the stages in sequence. All except the $out and $geoNear stages can appear multiple times in a pipeline. 

db.collection.aggregate( [ { <stage> }, ... ] ) 

