Idk, I feel it's missing really useful convenience stuff that exists here and there...

Examples, from the top of my head:

1. JOIN USING, for databases that support it. In some databases you can replace

    FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t1.c2 = t2.c2 ...

with

    FROM t1 JOIN t2 USING (c1, c2)

much shorther and cleaner

2. Ability to exclude columns in select *

DuckDB:

    SELECT * EXCLUDE (c1)

Spanner

    SELECT * EXCEPT (c1)