SQLite

Consider the following test case:

CREATE TABLE t0(c0);
CREATE INDEX i0 ON t0((0 AND (SELECT 1))); -- unexpected: no error
ALTER TABLE t0 RENAME COLUMN c0 TO c1; -- error in index i0: subqueries prohibited in index expressions

The test case demonstrates that the error reporting for subqueries in index expression is inconsistent. The CREATE INDEX succeeds, while an error for the subquery is raised by the ALTER TABLE. I would expect that either both raise an error, or allow the subquery.

This happens because "0 AND anything" gets converted into just "0" by the parser, long before the code ever reaches semantic analysis.

I don't think this is something we want to fix, because it would be a performance reduction and a complexity increase, all of the sake of "consistent error messages". However, I will take the suggestion under advisement...

In this case, it's probably not worth to further pursue this. In practice, the chances that someone relies on an error message in this case is probably minuscule.