Question

这是我的问题：

SELECT  GENRE,MAX(COUNT(GENRE)) 
FROM BOOKS
WHERE ID_BOOK IN(SELECT ID_BOOK 
                 FROM SIGNATURES
                 WHERE SIGNATURE IN(SELECT SIGNATURE 
                                    FROM ORDERS 
                                    WHERE ID_READER=1))
GROUP BY GENRE;

我收到错误：

SQL错误：ORA-00937：不是单组组功能

当我删除保留在SELECT之后的GENRE时它可以正常工作但只生成数字。我还需要知道哪个特定的GENRE具有最大值。

编辑：

select GENRE,CNT INTO var_genre, var_max from (
SELECT GENRE,COUNT(GENRE) as CNT FROM BOOKS
WHERE ID_BOOK IN(SELECT ID_BOOK FROM SIGNATURES
WHERE SIGNATURE IN(SELECT SIGNATURE FROM ORDERS WHERE ID_READER=1))
GROUP BY GENRE
order by COUNT(GENRE) desc)
where rownum < 2;

Answer 1

您无法在一个查询中进行聚合。你应该在子查询中做到这一点：

select distinct GENRE,CNT from ( 
  select GENRE,CNT, DENSE_RANK() Over(prder by CNT) as rnk from (
    SELECT GENRE,
           COUNT(GENRE) over (partition by GENRE) as CNT
      FROM BOOKS
     WHERE ID_BOOK IN(SELECT ID_BOOK 
                       FROM SIGNATURES
                       WHERE SIGNATURE IN(SELECT SIGNATURE FROM ORDERS WHERE ID_READER=1))
)
whre rnk = 1;

或者，如果您只需要一行，则可以将其包装到子查询中：

select GENRE,CNT from (
SELECT GENRE,COUNT(GENRE) as CNT FROM BOOKS
WHERE ID_BOOK IN(SELECT ID_BOOK FROM SIGNATURES
    WHERE SIGNATURE IN(SELECT SIGNATURE FROM ORDERS WHERE ID_READER=1))
GROUP BY GENRE
order by COUNT(GENRE) desc)
whre rownum < 2;

使用max（）进行复杂查询;

1 个答案: