> It's common in modern APIs to ask for a selective, minimal number of columns and also calculate derived information to display on a page Yes, but still for c

> It's common in modern APIs to ask for a selective, minimal number of columns and also calculate derived information to display on a page Yes, but still for common OLTP use cases you're only interested in a very small amount of data, say, the purchase orders of one customer. Whereas for OLAP, your queries touch on vast amounts of data, e.g. all purchase orders by month and product category. That's why typically a row-based storage model makes sense for OLTP, whereas for OLAP typically column-oriented models make sense.