Question

在下面的代码中，我想只在group by条件中给出的三列上应用组函数。但它给出了错误，错误的参数数量。

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Answer 1

你的意思是这样吗？

SELECT * FROM (
    SELECT
        a.id,
        a.name,
        c.code,
        a.active_dt,
        a.inactive_dt,
        b.category,
        COUNT(1) OVER(PARTITION BY a.id, a.name, c.code) AS CNT
    FROM
        student a,
        class b,
        descrip c
    WHERE
        a.id=b.id AND
        a.id=c.id
)
WHERE CNT > 1

Answer 2

如果我理解得很好，你只需要这个：

select a.id,a.name,  
       c.code,
       a.active_dt,
       a.inactive_dt,
       b.category,
       count(*) count
from student a,class b, descrip c
where a.id=b.id
and a.id=c.id
group by a.id,a.name,c.code
    having count(*) >1;

count()广告group by如何运作的一个小例子：

create table testGroup(a, b, c) as ( 
select 1, 2, 3 from dual union all
select 1, 2, 3 from dual union all
select 5, 6, 7 from dual union all
select 5, 6, 7 from dual union all
select 5, 6, 9 from dual union all
select 1, 2, 9 from dual 
)

您需要在群组中使用的列数不会影响您使用计数的方式;说你需要按3列分组：

SQL> select a, b, c, count(*)
  2  from testGroup
  3  group by a, b, c
  4  having count(*) > 1;

         A          B          C   COUNT(*)
---------- ---------- ---------- ----------
         5          6          7          2
         1          2          3          2

如果您只需要汇总2列：

SQL> select a, b, count(*)
  2  from testGroup
  3  group by a, b
  4  having count(*) > 1;

         A          B   COUNT(*)
---------- ---------- ----------
         5          6          3
         1          2          3

这假设您需要计算行数，无论值是否为空。

Answer 3

试试这个：

SELECT a.id, a.name, c.code, a.active_dt, a.inactive_dt, b.category, 
       count(DISTINCT a.id,a.name,c.code) [count]
FROM student a
INNER JOIN class b
    ON a.id=b.id
INNER JOIN descrip c
    ON a.id=c.id
GROUP BY a.id, a.name, c.code, a.active_dt, a.inactive_dt, b.category
HAVING count(a.id,a.name,c.code) > 1

如何在下面的查询中使用'GROUP BY'功能

3 个答案: