Showing specific output data based on duplicate rows and null values [postgresql] - sql

Question

I'm using the following SQL (with a union to two similar queries):
SELECT
distinct a.source,
a.p_id,
a.name,
b.prod_count,
b.prod_amt,
'Def' as prod_type
FROM
dwh.attribution_product_count a
LEFT OUTER JOIN
(
SELECT
distinct source,
p_id,
name,
sum(acct_count) as prod_count,
sum(acct_amt) as prod_amt
FROM
dwh.prod_count
WHERE
month = 3 AND
default_banner_flag = 0 AND
loan_flag = 3
GROUP BY
source,
name,
p_id ) as b
ON
a.p_id = b.p_id
UNION
SELECT
distinct a.source,
a.p_id,
a.name,
b.prod_count,
b.prod_amt,
'Other' as prod_type
FROM
dwh.attribution_product_count a
LEFT OUTER JOIN
(
SELECT
distinct source,
p_id,
name,
sum(acct_count) as prod_count,
sum(acct_amt) as prod_amt
FROM
dwh.prod_count
WHERE
month = 3 AND
default_banner_flag = 1 AND
loan_flag = 3
GROUP BY
source,
name,
p_id
ORDER BY
name ) as b
ON
a.p_id = b.p_id
The output I'm getting looks like this:
Essentially since FakeName #2 has one row showing actual numbers (not null), I ONLY want FakeName #2 to show up. This means I also want the null row for FakeName #2. But, since FakeName #1 and #3 have 2 null rows, I don't need them to show. What type of SQL command (or edit to my query) can accomplish this?

Answer 1

Firstly, if I read your query correctly, you can eliminate the need for a UNION by using CASE and IN. You also have a couple of bogus DISTINCTs in there (since you're using GROUP BY anyway). That gives:
SELECT DISTINCT
a.source,
a.p_id,
a.name,
b.prod_count,
b.prod_amt,
Case When default_banner_flag = 0 Then 'Def' Else 'Other' End as prod_type
FROM
dwh.attribution_product_count a
LEFT OUTER JOIN
(
SELECT
source,
p_id,
name,
default_banner_flag,
sum(acct_count) as prod_count,
sum(acct_amt) as prod_amt
FROM
dwh.prod_count
WHERE
month = 3 AND
default_banner_flag in (0, 1) AND
loan_flag = 3
GROUP BY
source,
name,
p_id,
default_banner_flag
) as b
ON
a.p_id = b.p_id
However, what you actually want is information about those p_ids which have at least one row in dwh.prod_count, so I think you can change your whole query around to use that as the sub-select:
SELECT
a.source,
a.p_id,
a.name,
sum(acct_count) as prod_count,
sum(acct_amt) as prod_amt,
Case When default_banner_flag = 0 Then 'Def' Else 'Other' End as prod_type
FROM
dwh.attribution_product_count a
LEFT OUTER JOIN
dwh.prod_count b
On a.p_id = b.p_id
INNER JOIN
(
SELECT DISTINCT
p_id
FROM
dwh.prod_count
WHERE
month = 3 AND
default_banner_flag in (0, 1) AND
loan_flag = 3
) as c
ON a.p_id = c.p_id
WHERE
month = 3 AND
default_banner_flag in (0, 1) AND
loan_flag = 3
(You could also rewrite this as a WHERE p_id IN ( sub-select ) or with a little fiddling WHERE EXISTS ( ... ), but this seemed the easiest version to demonstrate.)
Note that I haven't actually tested any of these queries, but I think they're logically sound.