SQL 分组查询如何实现动态分组？

SELECT 
  CASE WHEN :group_by = 'dept' THEN dept ELSE level END AS group_key,
  SUM(salary) AS total_salary
FROM employees
GROUP BY 
  CASE WHEN :group_by = 'dept' THEN dept ELSE level END;

SELECT 
  dept,
  CASE WHEN :with_month = 1 THEN sale_month ELSE 'ALL' END AS month_group,
  SUM(amount) AS total_amount
FROM sales
GROUP BY 
  dept,
  CASE WHEN :with_month = 1 THEN sale_month ELSE 'ALL' END;

group_fields = []
if by_dept: group_fields.append("dept")
if by_year: group_fields.append("EXTRACT(YEAR FROM order_date)")
if by_region: group_fields.append("region")

group_clause = ", ".join(group_fields)
sql = f"SELECT {', '.join(group_fields)}, SUM(amount) FROM orders GROUP BY {group_clause}"

DELIMITER //
CREATE PROCEDURE DynamicGroup(IN group_type VARCHAR(20))
BEGIN
  SET @sql = CONCAT('SELECT ', 
    CASE group_type 
      WHEN 'dept' THEN 'dept'
      WHEN 'month' THEN 'MONTH(order_date)'
      WHEN 'dept_month' THEN 'dept, MONTH(order_date)'
      ELSE '1'
    END,
    ', SUM(amount) FROM sales GROUP BY ',
    CASE group_type 
      WHEN 'dept' THEN 'dept'
      WHEN 'month' THEN 'MONTH(order_date)'
      WHEN 'dept_month' THEN 'dept, MONTH(order_date)'
      ELSE '1'
    END
  );
  PREPARE stmt FROM @sql;
  EXECUTE stmt;
  DEALLOCATE PREPARE stmt;
END //
DELIMITER ;