Can I modify this query using a WITH clause? - sql

Question

I have written the following query in order to achieve the following:
1) Select all regulatory languages that do not have a specified ID.
2) Link those regulatory languages based on a hierarchy field (RL_ID_DEFINED - this field is the ID of the parent regulatory language).
My first variation used NOT IN, but after looking into it I decided that NOT EXISTS would be a more efficient approach. Additionally, I was thinking that adding a WITH clause might make it run a bit faster, since in my current code it is running the nested SELECT statement for each ID in the iteration. Would it be possible to rewrite with using a WITH clause for that nested SELECT?
SELECT
T1.ID
FROM
REGULATORY_LANGUAGES T1
WHERE
T1.INACTIVE_DATE IS NULL
AND NOT EXISTS (
SELECT
NULL
FROM
REGULATORY_LANGUAGES T2,
REVIEW_REGULATIONS T3
WHERE
T3.RVWTYPYR_ID = ?
AND T3.RL_ID = T2.ID
AND T1.ID = T2.ID)
START WITH
RL_ID_DEFINED IS NULL
AND INACTIVE_DATE IS NULL
CONNECT BY
PRIOR ID = RL_ID_DEFINED
The problem I'm running into is that when I look at the structure of a WITH clause, I would be creating it prior to my main SELECT. However, that would require me to have defined my T1 table already. Any thoughts?
(Note - this is being called in a java method, hence the ? in the line T3.RVWTYPYR_ID = ?. When I test this in the database editor via Toad, I just hard code a value for the ?).

Answer 1

While speed is important, so is accuracy. You mentioned that you switched from not in to not exists for efficiency. They do different things. There is another way to speed up the logic of not in. Instead of this:
where someField not in
(select someField
from etc
)
Do this
where someField in
(select someField
from etc
where whatever
minus
select someField
from etc
where whatever
and more filters that identify records to exclude
)
Now for the with keyword. It speeds up performance when you want to run the exact same subquery more than once. So, instead of this:
where field1 in
(sql for subquery)
and field 2 in
(exact same sql as above)
you do this:
with temp as (sql for subquery)
select etc
where field1 in
(select something from temp)
and field 2 in
(select something from temp)
However, that's not your situation. What you probably want to do is to investigate ways to send a list of parameters from java so that your query looks like this:
T3.RVWTYPYR_ID in (?,?,etc)
Then you wouldn't have to repeat the subquery.

Answer 2

Much thanks to Tom H for his insight. I've rewritten the query using JOIN:
SELECT
T1.ID
FROM
REGULATORY_LANGUAGES T1
LEFT JOIN (
SELECT
T2.ID ID
FROM
REGULATORY_LANGUAGES T2
INNER JOIN
REVIEW_REGULATIONS T3
ON
T3.RVWTYPYR_ID = ?
AND T3.RL_ID = T2.ID) T_JOIN
ON T1.ID = T_JOIN.ID
WHERE
T1.INACTIVE_DATE IS NULL
AND T_JOIN.ID IS NULL
START WITH
T1.RL_ID_DEFINED IS NULL
AND T1.INACTIVE_DATE IS NULL
CONNECT BY
PRIOR T1.ID = T1.RL_ID_DEFINED