Why the following statement is erroneous?
SELECT dept_name, ID, avg (salary)
GROUP BY dept_name;
a) Dept_id should not be used in group by clause
b) Group by clause is not valid in this query
c) Avg(salary) should not be selected
Correct option: A
Any property that does not occur in the group by clause must only appear in an aggregate function if it also appears in the select clause; otherwise, the query is considered incorrect.
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