http://docs.mongodb.org/manual/reference/sql-comparison/
SQL Terms/Concepts MongoDB Terms/Concepts database database table collection row document or BSON document column field index index table joins embedded documents and linking
primary key
Specify any unique column or column combination as primary key.
In MongoDB, the primary key is automatically set to the_id field.
aggregation (e.g. group by)
aggregation pipeline
See the SQL to Aggregation Mapping Chart.
