SQL语言——有没有办法写两次平均值？

Question

问题是“列出所有大于平均付款两倍的付款”

SELECT AVG(amount)
FROM Payments
WHERE amount > AVG(amount)*2;

Answer 1

您需要一个子查询来计算总体平均金额：

SELECT * 
FROM Payments 
WHERE amount > (SELECT AVG(amount)*2 FROM Payments)