Question

Listagg函数在子查询中使用时不起作用，尽管在prod列中使用listagg函数并不连接单行中的所有产品

select
    a.id,
    a.num,
    (listagg(c.prod_name,',') within group(order by prod_name)
from product c
where c.prod_id = NVL(b.prod_id,b.prod_pos) As prod
from master a, base_product b
where
    b.id = a.id and
    b.type = 1 and
    a.id = 12345;

Answer 1

select子句中的子查询缺少select关键字，这可能是错误的直接来源。但是，我们可以改进您的查询，而是加入一个执行聚合的子查询：

select
    a.id,
    a.num,
    coalesce(c.prod, 'NA') as prod
from master a
inner join base_product b
    on b.id = a.id
left join
(
    select listagg(prod_name, ',') within group(order by prod_name) as prod
    from product
) c
    on c.prod_id = NVL(b.prod_id, b.prod_pos) 
where
    b.type = 1 and
    a.id = 12345;

除了重新调用listagg之外，我还使用显式inner join替换了隐式连接语法。这是编写查询的首选方式，这种风格是25年前ANSI SQL标准的一部分。

Answer 2

您可以在cte或派生表中的listagg(prod, ',') within group(ORDER BY prod)列上使用group by，并将其加入主表，以获取num，如下所示。

id

OR

SELECT t2.id,
       t2.num,
       t1.prod
FROM
  (SELECT num,
          listagg(prod, ',') within group(
                                          ORDER BY prod) AS prod
   FROM table1
   GROUP BY num ) t1
JOIN table1 t2 ON t1.num = t2.num
order by t2.id\\

给你样本数据：

WITH t1 AS
  (SELECT num,
          listagg(prod, ',') within group(
                                          ORDER BY prod) AS prod
   FROM table1
   GROUP BY num)
SELECT t2.id,
       t2.num,
       t1.prod
FROM t1
JOIN table1 t2 ON t1.num = t2.num
ORDER BY t2.id\\

<强>结果：

ID  NUM         PROD
--------------------
101 1701A001    book
102 1701A001    data
103 1702B005    bat
104 1702B005    ball
105 1703C006    Stumps

<强> DEMO

Listagg函数在子查询中不起作用

2 个答案: