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我的 SELECT 语句中有一个返回多行的子查询，但我需要这两个值。无论如何用逗号连接多个值以使外部查询认为子查询只返回一个值？

我的查询示例：

select o.id,
   (select v.value v from values v join attributes a on v.att_id=a.att_id where a.att_id='100' and v.id=o.id)
from objects o
where o.class_id='GGzX';

提前致谢！

4

3 回答 3

3

试试这个查询，也许会有用（点击这里测试查询）：

CREATE TABLE TEST1(
ID INT);

CREATE TABLE TEST2(
    ID INT,
    TXT VARCHAR2(100));

INSERT INTO TEST1 VALUES(1);
INSERT INTO TEST1 VALUES(2);
INSERT INTO TEST1 VALUES(3);

INSERT INTO TEST2 VALUES(1,'A');
INSERT INTO TEST2 VALUES(1,'B');
INSERT INTO TEST2 VALUES(2,'C');
INSERT INTO TEST2 VALUES(3,'A');
INSERT INTO TEST2 VALUES(3,'B');
INSERT INTO TEST2 VALUES(3,'C');

/* HERE IS THE QUERY!!!*/
SELECT A.ID, 
(SELECT listagg(B.TXT,',' ) WITHIN GROUP (ORDER BY B.ID)
FROM TEST2 B WHERE B.ID = A.ID
) AS CONTATENATED_FIELD
FROM TEST1 A;

注意：listagg 适用于 11.X 版本，请参阅此链接了解更多信息。

根据您的查询，您可能需要这样的东西：

select o.id,
(SELECT listagg(v.value,',' ) WITHIN GROUP (ORDER BY v.value) from values v join attributes a on v.att_id=a.att_id where a.att_id='100' and v.id=o.id)
from objects o
where o.class_id='GGzX';
于 2013-07-10T21:11:28.717 回答
0

只需添加GROUP BY a.att_id或限制您的查询

select o.id,
   (select v.value val from values v join attributes a on v.att_id=a.att_id
 where a.att_id='100' and v.id=o.id GROUP BY a.att_id)
from objects o
where o.class_id='GGzX';

OR


select o.id,
   (select v.value val from values v join attributes a on v.att_id=a.att_id
 where a.att_id='100' and v.id=o.id LIMIT 1)
from objects o
where o.class_id='GGzX';

或者只是按任何分隔符对值进行分组

select o.id,
   (select group_concat( v.value SEPARATOR ' / ') val from values v join attributes a on v.att_id=a.att_id
 where a.att_id='100' and v.id=o.id GROUP BY a.att_id)
from objects o
where o.class_id='GGzX';
于 2013-07-10T21:07:34.430 回答