Filtering subquery results - sql

Question

I'm having a problems filtering the duplicate values from my query. This is my query
SELECT cid.IDS_NO,cid.SUB_TITLE,cid.E_SUB_NAME, (cid.SUB_TITLE || ' '|| cid.E_SUB_NAME),
(SELECT(INST_BLK_HSE || ' ' || (SELECT E_STREET_NAME FROM street_table where street_code = d.INST_ST_CODE))
FROM del d where d.IDS_NO = cid.IDS_NO and ROWNUM = 1),
(SELECT INST_ST_LEVEL || '-' || INST_STUNIT FROM detail d where d.IDS_NO = cid.IDS_NO and rownum = 1),
('COUNTRY' ||' ' || pl_post),pl_post
FROM SUBSCRIBER cid where pl_postal_district = 15 and rownum < 3001
and hi_property_type IN ('CONDO','COMMERCIAL BUILDING');
These are the parts I'm having problems with:
(SELECT(INST_BLK_HSE || ' ' || (SELECT E_STREET_NAME FROM street_table where street_code = d.INST_ST_CODE))
FROM del d where d.IDS_NO = cid.IDS_NO and ROWNUM = 1),
(SELECT INST_ST_LEVEL || '-' || INST_STUNIT FROM detail d where d.IDS_NO = cid.IDS_NO and rownum = 1);
These parts always get multiple records, and I want to get only 1 record with the lowest sequence number, So here's what I did:
(SELECT(INST_BLK_HSE || ' ' || (SELECT E_STREET_NAME FROM street_table where street_code = d.INST_ST_CODE))
FROM del d where d.IDS_NO = cid.IDS_NO and ROWNUM = 1 ORDER BY d.SEQ_NO DESC),
(SELECT INST_ST_LEVEL || '-' || INST_STUNIT FROM detail d where d.IDS_NO = cid.IDS_NO and rownum = 1 ORDER BY d.SEQ_NO DESC);
But I always get an error saying missing parenthesis, but when I remove the order by, it works fine. What should I do to get my query running correctly?

Answer 1

Formatting your query to make it easier to read goes a long way to begin with.
But you also have a rather tricky problem, since you ..
want to get only 1 record with the lowest sequence number.
Should work like this:
SELECT s.ids_no
,s.sub_title
,s.e_sub_name
,(s.sub_title || ' '|| s.e_sub_name) AS title_sub_name
,d.some_col_name
,t.inst_name
,('COUNTRY' ||' ' || s.pl_post) AS country_post
,s.pl_post
FROM subscriber s
LEFT JOIN (
SELECT d.ids_no
,(d.inst_blk_hse || ' ' || st.e_street_name) AS some_col_name
,ROW_NUMBER() OVER (PARTITION BY d.ids_no ORDER BY d.seq_no) AS rn
FROM del d
LEFT JOIN e_street_name st ON st.street_code = d.inst_st_code
) d ON d.ids_no = s.ids_no AND d.rn = 1
LEFT JOIN (
SELECT ids_no
,(inst_st_level || '-' || inst_stunit) AS inst_name
,ROW_NUMBER() OVER (PARTITION BY d.ids_no ORDER BY d.seq_no) AS rn
FROM detail
) t ON t.ids_no = s.ids_no AND t.rn = 1
WHERE s.pl_postal_district = 15
AND s.rownum < 3001
AND s.hi_property_type IN ('CONDO','COMMERCIAL BUILDING');
More details on how the subqueries work under this related question:
Select first row in each GROUP BY group?
The core features is ROW_NUMBER() to get the record with the lowest sequence number.
I rewrote your correlated subqueries, because they generally suck performance-wise. They are also hard to read.
I use LEFT JOIN, so you still get a row in case the subquery shouldn't find anything to match.

Answer 2

Subqueries must return only one row. So you have to add rownum = 1 to the subquery that is inside the subquery FROM del d. Something like:
SELECT
cid.IDS_NO,
cid.SUB_TITLE,
cid.E_SUB_NAME,
(cid.SUB_TITLE || ' '|| cid.E_SUB_NAME),
(SELECT (INST_BLK_HSE || ' ' || (SELECT E_STREET_NAME
FROM street_table
where street_code = d.INST_ST_CODE
and rownum = 1)) <<<<<<< here
FROM del d
where d.IDS_NO = cid.IDS_NO
and ROWNUM = 1),
(SELECT INST_ST_LEVEL || '-' || INST_STUNIT
FROM detail d
where d.IDS_NO = cid.IDS_NO
and rownum = 1),
('COUNTRY' ||' ' || pl_post),
pl_post
FROM SUBSCRIBER cid
where pl_postal_district = 15
and rownum < 3001
and hi_property_type IN ('CONDO','COMMERCIAL BUILDING');
Or, JOIN all the tables like this:
SELECT
cid.IDS_NO,
cid.SUB_TITLE,
cid.E_SUB_NAME,
cid.SUB_TITLE || ' '|| cid.E_SUB_NAME,
d.INST_BLK_HSE || ' ' || s.E_STREET_NAME,
d.INST_ST_LEVEL || '-' || d.INST_STUNIT
'COUNTRY' ||' ' || pl_post),
pl_post
FROM SUBSCRIBER cid
INNER JOIN del d ON d.IDS_NO = cid.IDS_NO
INNER JOIN detail d2 ON d2.IDS_NO = cid.IDS_NO
INNER JOIN street_table s ON s.street_code = d.INST_ST_CODE
WHERE cid.pl_postal_district = 15
and cid.rownum < 3001
and cid.hi_property_type IN ('CONDO','COMMERCIAL BUILDING')
and s.rownum = 1
and d.rownum = 1
and d2.rownum = 1;