On the topic of nested CSV, three approaches: - treat it as a join, and unroll by duplicating non-nested CSV data in separate rows for every element in the nes

On the topic of nested CSV, three approaches: - treat it as a join, and unroll by duplicating non-nested CSV data in separate rows for every element in the nested CSV - treat it as a projection, have an extraction operator to project the cells you want - treat it as text substitution problem; I've seen CSV files where every line of CSV was quoted like it was a single cell in a larger CSV row You get nested CSV because upstream systems are often master/detail or XML but need to use CSV because everybody understands CSV because it's such a simple file format. Good stuff.