SELECT clause includes columns that are neither grouped nor wrapped in aggregate functions.
Standard SQL requires every non-aggregated column in the `SELECT` list to be present in the `GROUP BY` clause.
Selecting individual attributes alongside aggregate functions like `COUNT()` or `SUM()` without adding those attributes to `GROUP BY`.
1SELECT department_id, employee_name, AVG(salary)2FROM employees3GROUP BY department_id; -- ERROR: column "employees.employee_name" must appear in the GROUP BY clause1-- Fix 1: Add all selected columns to GROUP BY2SELECT department_id, employee_name, AVG(salary)3FROM employees4GROUP BY department_id, employee_name;5 6-- Fix 2: Use aggregate function if individual name isn't needed7SELECT department_id, COUNT(*) AS emp_count, AVG(salary) AS avg_sal8FROM employees9GROUP BY department_id;Simulate standard system builds to trigger compiler trace records and track memory crashes locally.
Because multiple employees belong to the same `department_id`, the database cannot determine which `employee_name` to display for the aggregate average.