mysql怎么获取百分比

-- 创建示例表
CREATE TABLE sales (
    id INT AUTO_INCREMENT PRIMARY KEY,
    salesperson VARCHAR(50),
    amount DECIMAL(10, 2)
);

-- 插入示例数据
INSERT INTO sales (salesperson, amount) VALUES
('Alice', 1000),
('Bob', 1500),
('Alice', 2000),
('Charlie', 500);

-- 计算特定销售员的销售额占总销售额的百分比
SELECT 
    salesperson,
    (SUM(amount) / (SELECT SUM(amount) FROM sales) * 100) AS percentage
FROM 
    sales
GROUP BY 
    salesperson;

SELECT 
    salesperson,
    (SUM(amount) / CAST((SELECT SUM(amount) FROM sales) AS FLOAT) * 100) AS percentage
FROM 
    sales
GROUP BY 
    salesperson;

SELECT 
    salesperson,
    CASE 
        WHEN (SELECT SUM(amount) FROM sales) = 0 THEN 0
        ELSE (SUM(amount) / (SELECT SUM(amount) FROM sales) * 100)
    END AS percentage
FROM 
    sales
GROUP BY 
    salesperson;