Oracle SQL Developer - 引用嵌套 from 语句中的字段时出错

Question

对于以下查询，当引用“y”中的变量时，第 4 行出现错误。当我只使用“y.*”（第 5 行）时，查询成功运行，但是当我尝试从第 4 行中的指定字段（y.field1 作为 PRODUCT，y.field2 作为 PRODUCT_TYPE，y .entity，y.TYPE1）。对于输出，我希望首先列出这些字段以供视觉参考。

我有这种方法/逻辑适用于其他查询（因为我正在将此逻辑用于查询的多种变体和各种表）。但是，我认为这个问题在于我试图从我的联接语句中的表中引用字段。

(
select 
       -- categorization fields: 
       -- table2.field1 as PRODUCT, table2.field2 as PRODUCT_TYPE, table3.entity, table3.TYPE1
       y.field1 as PRODUCT,
       y.field2 as PRODUCT_TYPE,
       y.entity,
       y.TYPE1
       ,y.*
from   (
  select *
  from   (
    -- table references:
    select table1.*,
           row_number() over (
             partition by
             -- categorization fields: 
             table2.field1,
             table2.field2,
             table3.entity,
             table3.TYPE1 
             order by table3.entity
           ) as rn
    -- table references
    from   table1
    -- joins, links, and filtering: 
           inner join table6  on table1.field_1 = table6.code1
           inner join table5  on (table6.code = table5.code1)
                              AND (table6.code = table5.code) 
            left join table3  on table6.ent1 = table3.ent_code
            left join table2  on table1.extid = table2.extID
    where  table1.tdate between '01-APR-19' and '01-APR-21'
    AND    table1.refe NOT IN ('OFF')
  ) x
  -- sample rows:
  where rn <= 2
) y
);

如果有人有办法让我更好地指定这些字段来自哪些表，请告诉我。我希望我能做这样的事情：

y.table2.field1 as PRODUCT,
y.table2.field2 as PRODUCT_TYPE,
y.table3.entity,
y.table3.TYPE1

对不起，我没有可用的小提琴！

Answer 1

如果有人有办法让我更好地指定这些字段来自哪些表，请告诉我。

不要使用select *。相反，请使用列名并为其提供适当的别名，以便您知道它们的来源：

举个例子：

SELECT small_value,
       medium_value,
       big_value
FROM   (
  SELECT small.value  AS small_value,
         medium.value AS medium_value,
         big.value    AS big_value
  FROM   big
         CROSS JOIN medium
         CROSS JOIN small
)
WHERE  1 = 1

在您的查询中，除了在y 中使用SELECT * 或在x 中使用SELECT table1.*，您还可以命名列并为其赋予描述性别名。

在“y”中引用变量时，第 4 行出现错误。

(
select 
       -- categorization fields: 
       -- table2.field1 as PRODUCT, table2.field2 as PRODUCT_TYPE, table3.entity, table3.TYPE1

这是因为您看不到 TABLE2 或 TABLE3，因为您正在查看的唯一“视图”是别名为 y 的子查询。

如果您想查看这些列，则需要在 x 子查询中 SELECT 它们并将它们传递给每个后续的外部查询。

(
  select *
  from   (
    -- table references:
    select table1.field1 AS t1_product,
           table1.field2 AS t1_product_type,
           table1.entity AS t1_entity,
           table1.type1  AS t1_type1,
           table2.field1 AS t2_product,
           table2.field2 AS t2_product_type,
           table2.entity AS t2_entity,
           table2.type1  AS t2_type1,
           table3.field1 AS t3_product,
           table3.field2 AS t3_product_type,
           table3.entity AS t3_entity,
           table3.type1  AS t3_type1,
           row_number() over (
             partition by
             -- categorization fields: 
             table2.field1,
             table2.field2,
             table3.entity,
             table3.TYPE1 
             order by table3.entity
           ) as rn
    -- table references
    from   table1
    -- joins, links, and filtering: 
           inner join table6  on table1.field_1 = table6.code1
           inner join table5  on (table6.code = table5.code1)
                              AND (table6.code = table5.code) 
            left join table3  on table6.ent1 = table3.ent_code
            left join table2  on table1.extid = table2.extID
    where  table1.tdate between '01-APR-19' and '01-APR-21'
    AND    table1.refe NOT IN ('OFF')
  ) x
  -- sample rows:
  where rn <= 2
);