[wenc]

SQL does not exactly implement relational algebra in its pure form.

SQL implements a kind of set theory with relational elements and a bunch of practical features like pivots, window functions etc.

Pandas does the same. Most data frame libraries like dplyr etc. implement a common set of useful constructs. There’s not much difference in expressiveness. LINQ Is another language around manipulating sets that was designed with the help of category theory, and it arrives at the same constructs.

However SQL is declarative, which provides a path for query optimizers to parse and create optimized plans. Whereas with chained methods, unless one implements lazy evaluation one misses out on look aheads and opportunities to do rewrites.

[valw]

> There’s not much difference in expressiveness

> However SQL is declarative

Pick one :) the way I see it, if declarativeness is not a factor in assessing expressiveness, then expressiveness reduces to the uninteresting notion of Turing-equivalence.

[wenc]

Expressiveness and declarativeness are different things, no?

Are you talking about aesthetics? I’ve used SQL for 20 years and it’s elegant in parts but it also has warts. I talk about this elsewhere but SQL gets repetitive and requires multi layer CTEs to express certain simple aggregations.