This article has its amount of religious bias and wishful thinking. The author tries to establish his base on a fact that SQL is all about relational algebra and it's the right paradigm to query your data. While I agree with the latter, the author (and lots of other people) seems to forget that SQL is a dumbed-down-aimed-to-mediocre-programmers contraption inspired by relational algebra, but not really properly relational! It's really far from what Codd had in mind. If you read the history of early SQL dialects and DB2 vs Oracle competition it's clear that SQL was marketed as a language everyone can program in (thus the stupid imitation of a natural language) -- we know in XXI century that this is a bs...

I'd say that SQL is a COBOL of relational algebra...