帮我编写 mySQL 查询语句,分析三个月复购率，复购金额，复购人数，购买金额，购买人数，，按月移动，非季度

假设你的表名为 `orders`，包含以下字段：`order_id`（订单ID），`user_id`（用户ID），`order_time`（下单时间），`order_amount`（订单金额）。

以下是计算三个月复购率、复购金额、复购人数、购买金额、购买人数的 mySQL 查询语句，按月移动：

SELECT
    DATE_FORMAT(order_time, '%Y-%m') AS month,
    COUNT(DISTINCT CASE WHEN DATEDIFF(order_time, first_order_time) <= 90 AND repeat_count > 0 THEN user_id END) / COUNT(DISTINCT CASE WHEN DATEDIFF(order_time, first_order_time) <= 90 THEN user_id END) AS repeat_rate,
    SUM(CASE WHEN DATEDIFF(order_time, first_order_time) > 90 AND repeat_count > 0 THEN order_amount ELSE 0 END) AS repeat_amount,
    COUNT(DISTINCT CASE WHEN DATEDIFF(order_time, first_order_time) > 90 AND repeat_count > 0 THEN user_id END) AS repeat_count,
    SUM(CASE WHEN DATEDIFF(order_time, first_order_time) <= 90 THEN order_amount ELSE 0 END) AS purchase_amount,
    COUNT(DISTINCT CASE WHEN DATEDIFF(order_time, first_order_time) <= 90 THEN user_id END) AS purchase_count
FROM (
    SELECT
        order_id,
        user_id,
        order_time,
        order_amount,
        MIN(order_time) OVER (PARTITION BY user_id) AS first_order_time,
        COUNT(*) OVER (PARTITION BY user_id) - 1 AS repeat_count
    FROM orders
) t
GROUP BY DATE_FORMAT(order_time, '%Y-%m')
ORDER BY month;

解释一下查询语句：

1. `MIN(order_time) OVER (PARTITION BY user_id)` 表示每个用户的第一次下单时间；
2. `COUNT(*) OVER (PARTITION BY user_id) - 1` 表示每个用户的下单次数减去第一次下单，即复购次数；
3. `CASE WHEN DATEDIFF(order_time, first_order_time) <= 90 AND repeat_count > 0 THEN user_id END` 表示三个月内有复购的用户ID；
4. `CASE WHEN DATEDIFF(order_time, first_order_time) > 90 AND repeat_count > 0 THEN order_amount ELSE 0 END` 表示三个月后有复购的订单金额；
5. `CASE WHEN DATEDIFF(order_time, first_order_time) <= 90 THEN order_amount ELSE 0 END` 表示三个月内下的订单金额。

注意：上面的查询语句计算复购率时使用的是用户数，而不是订单数。计算复购率时，需要先确定每个用户的第一次下单时间，然后根据三个月内是否有复购来决定该用户是否算作复购用户。