There is of course sql.. and
PRQL — Pipelined Relational Query Language, pronounced “Prequel”. The web page has good examples and the advantages; probably the most promising looking of these query languages I have known so far (aug 2023).
And there is hydromatic/morel: Standard ML interpreter, with relational extensions, implemented in Java.. the reasoning behind the creation of Morel is given here — Morel: A functional language for data | Julian Hyde on Streaming Data, Open Source OLAP. And stuff.. The creator of Morel is also behind Apache Calcite, Mondrian (OLAP tool, IIRC).