题解 | #分析客户逾期情况#

WITH T1 AS (

SELECT C.customer_id, C.pay_ability, L.overdue_days FROM customer_tb C
LEFT OUTER JOIN loan_tb L
ON C.customer_id=L.customer_id
)

SELECT pay_ability,
CONCAT(ROUND((COUNT(overdue_days)/COUNT(1))*100, 1), '%') AS overdue_ratio 
FROM T1
GROUP BY pay_ability
ORDER BY OVERDUE_RATIO DESC
;

左外连接可以将null也连接到左表中，先把底表联完存在临时表T1里

count（某列）是不会计算null值的，count（1）则不管是否null都会计入，所以两者相除，group by 等级ABC就可以得到要求的ratio

输出数字的格式 A/B默认是小数，0.66666这样，先*100，再用round留一位小数点，最后用concat加上%，就可以了