如何将mysql行转换为没有标签的列

CREATE TABLE sales (
    id INT AUTO_INCREMENT PRIMARY KEY,
    product VARCHAR(50),
    quarter VARCHAR(10),
    amount DECIMAL(10, 2)
);

INSERT INTO sales (product, quarter, amount) VALUES
('Product A', 'Q1', 100),
('Product A', 'Q2', 150),
('Product B', 'Q1', 200),
('Product B', 'Q2', 250);

SELECT product,
       SUM(CASE WHEN quarter = 'Q1' THEN amount ELSE 0 END) AS Q1,
       SUM(CASE WHEN quarter = 'Q2' THEN amount ELSE 0 END) AS Q2
FROM sales
GROUP BY product;

+------------+------+------+
| product    | Q1   | Q2   |
+------------+------+------+
| Product A  | 100  | 150  |
| Product B  | 200  | 250  |
+------------+------+------+

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'SUM(CASE WHEN quarter = ''',
      quarter,
      ''' THEN amount ELSE 0 END) AS ',
      quarter
    )
  ) INTO @sql
FROM sales;

SET @sql = CONCAT('SELECT product, ', @sql, ' FROM sales GROUP BY product');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;