用SQL计算客户级M1回收率

M1回收率是指1-30天逾期的贷款回收金额与总逾期贷款金额的比率，因此计算客户级M1回收率的SQL语句应该包含以下几个步骤：

1. 计算每个客户的逾期贷款金额和1-30天逾期的贷款回收金额。

SELECT customer_id, 
       SUM(CASE WHEN overdue_days <= 30 THEN loan_amount ELSE 0 END) AS m1_recovered_amount, 
       SUM(CASE WHEN overdue_days > 0 THEN loan_amount ELSE 0 END) AS total_overdue_amount
FROM loan_table
GROUP BY customer_id;

2. 计算每个客户的M1回收率。

SELECT customer_id, 
       (m1_recovered_amount / total_overdue_amount) AS m1_recovery_rate
FROM (
  SELECT customer_id, 
         SUM(CASE WHEN overdue_days <= 30 THEN loan_amount ELSE 0 END) AS m1_recovered_amount, 
         SUM(CASE WHEN overdue_days > 0 THEN loan_amount ELSE 0 END) AS total_overdue_amount
  FROM loan_table
  GROUP BY customer_id
) AS temp;

在以上SQL语句中，loan_table是包含贷款信息的表，包括贷款金额、逾期天数、客户ID等字段。首先使用第一条SQL语句计算每个客户的逾期贷款金额和1-30天逾期的贷款回收金额，然后使用第二条SQL语句计算每个客户的M1回收率。