Why SQL is not relational: Ordering, Namelessness, and Name Duplication

• In SQL, columns are ordered and can be referred to positionally
• Relational theory is clear that all attributes are referred to by name
• SQL allows for a query to return two columns with the same name
• SELECT Employee.department_id, Department.department_id ...
• SQL allows for a query to return columns without names
• SELECT SUM(salary) FROM Employee