Oracle SQL代码语法标准，错误“不是单组组函数”

Question

I have a block of Oracle SQL code that does work. I figured out I cannot get the cert column and the max(run_time) at the same time.

select
  cert,
  max(run_time)
from
  bond_films
where title in
(
'Casino Royale','On Her Majesty_s Secret Service','Licence to Kill'
);

I was reading a SQL reference and it has the following syntax, but I thought my code matches the syntax?

SELECT [column,] group_function(column)
FROM table
[WHERE condition]
[GROUP BY group_by_expression]
[HAVING group_condition]
[ORDER BY column] ;

Can someone explain this to me or suggest a source which says I cannot write a code like I did?

Answer 1

You need a GROUP BY clause because you have included the cert column. If you had only done SELECT MAX(run_time) it would not be necessary to supply a GROUP BY since you are selecting the maximum value of all rows. But, since you have requested another column ( cert ), Oracle expects that you want to retrieve the max value for each different cert .

select
  cert,
  max(run_time)
from
  bond_films
where title in ('Casino Royale','On Her Majesty_s Secret Service','Licence to Kill')
GROUP BY cert;