As a Google Analytics user you are probably quite attached to the default reports in the user interface of Universal Analytics. It can be hard to make sense of the data in the BigQuery export tables.
Let me enable you to replicate the reports you're familiar with. I'll try to keep it basic here.
In the Conversions | (Standard) Ecommerce | Transactions report you'll find data about the performance of your ecommerce activities, segmented by
-- this query will not return quantity data as there is no standard ecommerce product data available in the sample data set select hits.transaction.transactionid, ifnull(sum(hits.transaction.transactionrevenue)/1000000,0) as revenue, ifnull(sum(hits.transaction.transactiontax)/1000000,0) as tax, ifnull(sum(hits.transaction.transactionshipping)/1000000,0) as shipping, ifnull(sum(hits.item.itemquantity),0) as quantity from `bigquery-public-data.google_analytics_sample.ga_sessions_20160801`, unnest(hits) as hits where totals.visits = 1 and hits.transaction.transactionid is not null group by transactionid order by revenue desc