Question

我正在用LISTAGG编写一个ORACLE select语句。它有效，但是当我验证数据时，我看到了重复数据，如1：1,1：1,2：2,2：2。

我确认数据库确实有重复。该查询用于一对多关系中的两个表。下面是我的查询片段，但我更改了列名等。

如何修改以下查询以返回每个人的唯一值？

由于

SELECT Table1.PERSON_ID, 
       Table1.FIRST_NAME,
       Table1.MIDDLE_NAME,
       Table1.LAST_NAME,

LISTAGG(case  
        when Table2.DESCRIPTION = '1' then '1:1'
        when Table2.DESCRIPTION = '2' then '2:2'
        when Table2.DESCRIPTION = '3' then '3:3'
        when Table2.DESCRIPTION = '4' then '4:4'
        when Table2.DESCRIPTION = '5' then '5:5'
        when Table2.DESCRIPTION = '6' then '6:6'
        when Table2.DESCRIPTION = '7' then '7:7'
        when Table2.DESCRIPTION = '8' then '8:8'
        when Table2.DESCRIPTION = '9' then '9:9'


      else ''

 end, ',')  
WITHIN GROUP (ORDER BY Table2.DESCRIPTION )  

FROM Table1
LEFT JOIN Table2

ON Table2.PERSON_ID = Table1.PERSON_ID
GROUP BY Table1.PERSON_ID,Table1.FIRST_NAME,Table1.MIDDLE_NAME, Table1.LAST_NAME

Answer 1

在Oracle中，您需要在子查询中执行DISTINCT：

SELECT PERSON_ID, FIRST_NAME, MIDDLE_NAME, LAST_NAME,
        LISTAGG(val, ',') WITHIN GROUP (ORDER BY DESCRIPTION )
FROM (SELECT DISTINCT Table1.PERSON_ID, Table1.FIRST_NAME, Table1.MIDDLE_NAME, Table1.LAST_NAME, Table2.Description
             (case when Table2.DESCRIPTION = '1' then '1:1'
                   when Table2.DESCRIPTION = '2' then '2:2'
                   when Table2.DESCRIPTION = '3' then '3:3'
                   when Table2.DESCRIPTION = '4' then '4:4'
                   when Table2.DESCRIPTION = '5' then '5:5'
                   when Table2.DESCRIPTION = '6' then '6:6'
                   when Table2.DESCRIPTION = '7' then '7:7'
                   when Table2.DESCRIPTION = '8' then '8:8'
                   when Table2.DESCRIPTION = '9' then '9:9'
                   else ''
              end) as val
      FROM Table1 LEFT JOIN
           Table2
           ON Table2.PERSON_ID = Table1.PERSON_ID
     ) 
GROUP BY PERSON_ID, FIRST_NAME, MIDDLE_NAME, LAST_NAME;

Answer 2

假设Table2有PERSON_ID作为指向Table1的外键，您需要做的是替换

FROM Table1
LEFT JOIN Table2
ON Table2.PERSON_ID = Table1.PERSON_ID

与

FROM Table1
LEFT JOIN 
(SELECT DISTINCT PERSON_ID, DESCRIPTION FROM Table2) T2
ON T2.PERSON_ID = Table1.PERSON_ID

然后在Table2中将T2更改为LISTAGG()（包括在WITHIN GROUP (ORDER BY ...)子句中！）

Oracle LISTAGG案例返回不同的值

2 个答案: