Replace NULL with "N/A" - sql

Question

I'm trying to use the Oracle NVL() function to replace NULL with "N/A":
SELECT ID AS "Record ID",
( SELECT NVL( COMMENT , "N/A") FROM CHECKBOX WHERE ( B1_CHECKBOX_DESC = 'Solar KW' ) AND ( RECORDS.ID1 = CHECKBOX.ID1 AND RECORDS.ID3 = CHECKBOX.ID3 ) ) AS "Solar",
( SELECT NVL( COMMENT, "N/A" ) FROM CHECKBOX WHERE ( B1_CHECKBOX_DESC = 'Code Edition' ) AND ( RECORDS.ID1 = CHECKBOX.ID1 AND RECORDS.ID3 = CHECKBOX.ID3 ) ) AS "Coder"
FROM RECORDS
Note: I'm trying to replace NULL with "N/A," not an empty string, so it should work. However, in the result set, I'm still getting NULL values instead of "N/A". What am I doing wrong?

Answer 1

Just wrong place for NVL(), not that your subqueries may not return rows, so use NVL on subquery:
SELECT ID AS "Record ID",
NVL(
( SELECT "COMMENT" FROM CHECKBOX WHERE B1_CHECKBOX_DESC = 'Solar KW'
AND RECORDS.ID1 = CHECKBOX.ID1 AND RECORDS.ID3 = CHECKBOX.ID3 )
, 'N/A') AS "Solar",
NVL(
( SELECT "COMMENT" FROM CHECKBOX WHERE B1_CHECKBOX_DESC = 'Code Edition'
AND RECORDS.ID1 = CHECKBOX.ID1 AND RECORDS.ID3 = CHECKBOX.ID3 )
, 'N/A' ) AS "Coder"
FROM RECORDS
But probably it would be better to use lateral or outer apply here:
SELECT
ID AS "Record ID",
c.*
FROM RECORDS
outer apply(
SELECT
nvl(solar,'N/A') as solar,
nvl(coder,'N/A') as coder
FROM (select *
from CHECKBOX
WHERE B1_CHECKBOX_DESC in ('Solar KW' , 'Code Edition')
AND RECORDS.ID1 = CHECKBOX.ID1
AND RECORDS.ID3 = CHECKBOX.ID3
)
pivot(
max("COMMENT")
for B1_CHECKBOX_DESC in (
'Solar KW' as Solar,
'Code Edition' as Coder
)
)
) c
Full example with test data:
DBFiddle
with
records(id,id1,id3) as (
select 1,1,1 from dual union all
select 2,2,2 from dual
)
,CHECKBOX("COMMENT",id1,id3,B1_CHECKBOX_DESC) as (
select 'comment1-1',1,1, 'Solar KW' from dual union all
select 'comment1-2',1,1, 'Code Edition' from dual union all
select 'comment2-1',2,2, 'Solar KW' from dual
)
SELECT
ID AS "Record ID",
c.*
FROM RECORDS
outer apply(
SELECT
nvl(solar,'N/A') as solar,
nvl(coder,'N/A') as coder
FROM (select *
from CHECKBOX
WHERE B1_CHECKBOX_DESC in ('Solar KW' , 'Code Edition')
AND RECORDS.ID1 = CHECKBOX.ID1
AND RECORDS.ID3 = CHECKBOX.ID3
)
pivot(
max("COMMENT")
for B1_CHECKBOX_DESC in (
'Solar KW' as Solar,
'Code Edition' as Coder
)
)
) c;
Results:
Record ID SOLAR CODER
---------- ---------- ----------
1 comment1-1 comment1-2
2 comment2-1 N/A