SELECT中的MAX和AVG不起作用

Question

我有两个分开的查询：

SELECT avg(priv_even_price) FROM private_event;

输出

"AVG(PRIV_EVEN_PRICE)"        
"387.833333333333333333333333333333333333"

和

SELECT max(priv_even_price) FROM private_event;

输出

"MAX(PRIV_EVEN_PRICE)"        
"950"                

如果我将这两者合并，为什么它不起作用，我在以下查询中收到错误：

SELECT max(priv_even_price) - (SELECT avg(priv_even_price) FROM private_event)
FROM private_event;

ORA-00937: not a single-group group function
00937. 00000 -  "not a single-group group function"
*Cause:    
*Action:
Error at Line: 1 Column: 39

Answer 1

每次都不要写SELECT，只需将函数作为表达式的一部分调用。

SELECT MAX(priv_even_price) - AVG(priv_even_price)
FROM private_event;

Answer 2

试

SELECT
    (SELECT max(priv_even_price) FROM private_event)
  - (SELECT avg(priv_even_price) FROM private_event) AS Difference

Answer 3

SELECT max(priv_even_price)-avg(priv_even_price) "Difference" FROM private_event