Invalid error "not a valid GROUP BY expression" for prepared parameter with LOCAL column alias

Detail name	Value
Changelog Number	31180
Type	Bug
Status	Resolved
Affected Versions	Exasol 2026.1.0, Exasol 2025.2.1, Exasol 2025.1.10
Fix Versions	Exasol 2025.1.15
Resolution Date	2026-08-13

Description

A prepared statement can incorrectly return the error “not a valid GROUP BY expression” when all of the following conditions are met:

• A select-list expression contains a prepared parameter.
• The expression is assigned a column alias.
• The GROUP BY clause refers to that alias with LOCAL.

Example

-- Expected: one row
-- Observed: not a valid GROUP BY expression
SELECT c + ? AS c
FROM VALUES 1 t(c)
GROUP BY LOCAL.c;

Workaround

Remove LOCAL by moving the aliased expression into a sub-query, then group by the resulting column:

SELECT c
  FROM (
      SELECT c + ? AS c
      FROM VALUES 1 t(c)
  )
  GROUP BY c;

Fix

Prepared parameters are now correctly recognized when resolving LOCAL column aliases in GROUP BY clauses. The query succeeds and returns the expected result.