mysql行转列 合并字段

CREATE TABLE sales (
    id INT AUTO_INCREMENT PRIMARY KEY,
    product VARCHAR(50),
    region VARCHAR(50),
    sales_amount INT
);

SELECT 
    product,
    SUM(CASE WHEN region = 'North' THEN sales_amount ELSE 0 END) AS North,
    SUM(CASE WHEN region = 'South' THEN sales_amount ELSE 0 END) AS South,
    SUM(CASE WHEN region = 'East' THEN sales_amount ELSE 0 END) AS East,
    SUM(CASE WHEN region = 'West' THEN sales_amount ELSE 0 END) AS West
FROM 
    sales
GROUP BY 
    product;

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

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

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

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

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

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