oracle sql中的listagg

Question

我在Oracle中有以下sql查询：

SELECT listagg(A.name, ",") within group (ORDER BY A.id) as A,
listagg(B.name, ",") within group (ORDER BY B.id) as B
FROM some_table
join A on A.id = some_table.id
join B.name = some_table.name
where some_table.status in (1,2,3)
group by some_table.id

我的问题是我从listagg中得到了重复的结果，这是我不想要的。我怎么才能修复它呢？谢谢!

Answer 1

在Oracle19之前，Oracle不支持用于listagg()的distinct。

然而，在您的例子中，问题可能是由joins的笛卡尔乘积引起的。这表明相关子查询是更好的方法：

select t.*,
       (select listagg(a.name, ',') within group (order by a.id)
        from A a
        where a.id = t.id 
       ) as a,
       (select listagg(b.name, ',') within group (order by b.id)
        from B b
        where b.id = t.id 
       ) as b
from some_table t
where t.status in (1, 2, 3)
group by t.id;

Answer 2

Listagg函数不支持distinct选项。您应该使用子查询来选择唯一值。