As for myself, I wish SQL's SELECT were more expressive. It's currently organized almost exactly like a mirror of the underlying relational algebra operators that a query engine has to execute internally.

But relational operators isn't what developers like to work with. SQL is about "projecting" relations, putting them through some basic transforms, none of which compose that well because of SQL's statement-oriented syntax. For example, you can't group a group-by. A group-by takes a list of terms, but you can't funnel the output through another one without wrapping the whole query in a "SELECT FROM (...) AS ...".

I'd like a query language that more expressive, expression-based syntax where the results of each expression can be "piped" into the next step to perform transformations, joins, reductions and so on.