Question

我有两个表，客户和产品。

产品：

productid name
 1        pro1
 2        pro2
 3        pro3

客户：

id    name   productid
1     cust1  1,2
2     cust2  1,3
3     cust3

我要在select语句中关注结果，

id   name    productid
 1  cust1    pro1,pro2
 2  cust2    pro1,pro3
 3  cust3

我在两个表中都有300多个记录，我是初学者到后端编码，有帮助吗？

Answer 1

绝对不好的数据库设计，但坏的是您必须忍受这一点。这是我使用递归查询创建的解决方案。我看不到product表的使用，因为您的要求与product表无关。

with 
    --Expanding each row seperated by comma     
    tab(col1,col2,col3) as (                           
                             Select distinct c.id,c.prdname,regexp_substr(c.productid,'[^,]',1,level)
                              from customers c
                              connect by regexp_substr(c.productid,'[^,]',1,level) is not null
                              order by 1), 
     --Appending `Pro` to each value                          
     tab_final as            (  Select col1,col2, case when col3 is not null 
                                                  then 'pro'||col3
                                                  else col3
                                                  end col3
                            from tab )
 --Displaying result as expected                           
SELECT
    col1,
    col2,
    LISTAGG(col3,',') WITHIN GROUP( ORDER BY col1,col2 ) col3
FROM
    tab_final
GROUP BY
    col1,
    col2

演示：

--Preparing dataset  
 With                              
     customers(id,prdname,productid) as ( Select 1, 'cust1', '1,2' from dual
                               UNION ALL
                               Select  2,  'cust2','1,3' from dual
                               UNION ALL
                               Select 3,  'cust3','' from dual), 
    --Expanding each row seperated by comma                               
    tab(col1,col2,col3) as (                           
                             Select distinct c.id,c.prdname,regexp_substr(c.productid,'[^,]',1,level)
                              from customers c
                              connect by regexp_substr(c.productid,'[^,]',1,level) is not null
                              order by 1), 
     --Appending `Pro` to each value                          
     tab_final as            (  Select col1,col2, case when col3 is not null 
                                                  then 'pro'||col3
                                                  else col3
                                                  end col3
                            from tab )
 --Displaying result as expected                           
SELECT
    col1,
    col2,
    LISTAGG(col3,',') WITHIN GROUP( ORDER BY col1,col2 ) col3
FROM
    tab_final
GROUP BY
    col1,
    col2

PS：在使用时，请不要忘记将实际的表列放在我的示例中，这可能会有所不同。

根据逗号分隔的ID提取名称

1 个答案: