[anonacct37]

This is an overly simplistic but also correct answer: clickhouse was developed for analytics on clickstreams.

Technically the overall idea is that if you have lots of queries that only read certain columns and your database stores rows contiguously it's a waste to read a whole row and then discard columns.

Also compression (such as run length or delta or even ztsd) often works better if you give it a block of data that's from one column (such as a timestamp or tag value).