mysql 分表查询中间价

-- 查询所有分表的订单金额
SELECT amount
FROM (
    SELECT amount FROM orders_0
    UNION ALL
    SELECT amount FROM orders_1
    UNION ALL
    ...
    UNION ALL
    SELECT amount FROM orders_9
) AS all_orders
ORDER BY amount;

-- 计算中位数
SET @rownum := (SELECT COUNT(*) FROM (
    SELECT amount
    FROM (
        SELECT amount FROM orders_0
        UNION ALL
        SELECT amount FROM orders_1
        UNION ALL
        ...
        UNION ALL
        SELECT amount FROM orders_9
    ) AS all_orders
) AS total_rows);

SELECT AVG(amount)
FROM (
    SELECT amount
    FROM (
        SELECT amount FROM orders_0
        UNION ALL
        SELECT amount FROM orders_1
        UNION ALL
        ...
        UNION ALL
        SELECT amount FROM orders_9
    ) AS all_orders
    ORDER BY amount
    LIMIT @rownum DIV 2, 1
    UNION ALL
    SELECT amount
    FROM (
        SELECT amount FROM orders_0
        UNION ALL
        SELECT amount FROM orders_1
        UNION ALL
        ...
        UNION ALL
        SELECT amount FROM orders_9
    ) AS all_orders
    ORDER BY amount DESC
    LIMIT @rownum DIV 2, 1
) AS median_values;