Oracle SQL Developer - error when referencing fields within nested from statements - sql

Question

For the below query I am getting an error with line 4 when referencing variables within "y". The query runs successfully when I use just " y.* " (line 5), however it generates an error when I try to also pull from the specified fields in line 4 (y.field1 as PRODUCT, y.field2 as PRODUCT_TYPE, y.entity, y.TYPE1). For the output, I want these fields listed first for visual reference.
I have this approach/ logic working for other queries (as i'm re using this logic for multiple variations of queries and various tables). However, I think that the issue with this one lies in my attempt to reference fields from tables that are in my join statements.
(
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
);
Let me know if anyone has a way that I can maybe better specify which tables those fields come from. I wish I could just do something like this:
y.table2.field1 as PRODUCT,
y.table2.field2 as PRODUCT_TYPE,
y.table3.entity,
y.table3.TYPE1
Sorry that I don't have a fiddle available!

Answer 1

Let me know if anyone has a way that I can maybe better specify which tables those fields come from.
Don't use select *. Instead, use the column names and give them appropriate aliases so you know where they came from:
As an example:
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
In your query, instead of using SELECT * in y or using SELECT table1.* in x you can name the columns and give them descriptive aliases.
I am getting an error with line 4 when referencing variables within "y".
(
select
-- categorization fields:
-- table2.field1 as PRODUCT, table2.field2 as PRODUCT_TYPE, table3.entity, table3.TYPE1
That is because you cannot see TABLE2 or TABLE3 because the only "view" you are looking at is of the sub-query with the alias y.
If you want to see those columns then you need to SELECT them inside the x subquery and pass them to each subsequent outer-query.
(
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
);