With clause subquery availablility for the entire SQL statement in Oracle - sql

Question

I am trying to write a SQL statement which reuses the subquery of the With clause multiple times in Oracle.
With mySubQ as (
...
)
Select Something
From SomeTable,
(
Select *
From mySubQ
where mySubQ.Something >= 0
) newSubQ
where mySubQ.Something = SomeTable.Something
This gives me error - ORA-32034 unsupported use of WITH clause
What am I missing?

Answer 1

You need to join with mySubQ, not just define it.
WITH mySubQ AS (...)
SELECT Something
FROM SomeTable
JOIN mySubQ ON mySubQ.Something = SomeTable.Something
WHERE mySubQ.Something >= 0
If you put the query of mySubQ in a subquery, you can't reference mySubQ in the WHERE clause of the main query. Each level of query can only access tables in its own FROM and JOIN clauses, not those of subqueries.

Answer 2

Here is the error: where mySubQ.Something = SomeTable.Something.
The bottom query selects from SomeTable and from the subquery with alias newSubQ,
so mySubQ.Something is not known in this context.
If something is a real column name, not only a "placeholder in the pseudocode", then there is also another error here: Select Something - the column is ambiguous, because both sometable and the subquery have this column.
Try this query:
With mySubQ as (
SELECT * FROM sometable
)
Select newSubQ.Something
From SomeTable,
(
Select *
From mySubQ
where mySubQ.Something >= 0
) newSubQ
where newSubQ.Something = SomeTable.Something
;
Demo --> http://www.sqlfiddle.com/#!4/88855/12
This demo contains also another example of using WITH clause:
WITH mySubQ AS (
SELECT *
FROM sometable
),
mySubQ_1 AS (
SELECT *
FROM mySubQ
WHERE somethingelse = 1
),
mySubQ_2 AS (
SELECT *
FROM mySubQ
WHERE something between 2 AND 5
)
SELECT *
FROM sometable s, mySubQ_1 m1,
(
SELECT * FROM mySubQ_2
WHERE something < 10
) m2
WHERE s.something = m1.something
AND m1.somethingelse = m2.somethingelse