How to create a view from existing table records, but also adding new records that do not exist - sql

Question

I am trying to create a view from an existing views data, but also if there are certain lines that do not exist per part/date combo, then have those lines be created. I have the below query that is showing what I currently have for the particular s_date/part_no combos:
SELECT
s_date,
part_no,
issue_group,
s_level,
qty_filled
FROM
current_view
WHERE
part_no = 'xxxxx'
AND s_date IN (
'201802',
'201803'
)
ORDER BY
s_date,
part_no,
issue_group,
DECODE(s_level, '80', 1, '100', 2, 'Late', 3)
Which produces the below:
I know how to create a view with that data, that's the easy part. But what I'm needing is a line for each issue_group and s_level combo, and if it's a created line, to put 0 as the qty_filled.
Every part_no / s_date combo should have 6 rows that go with it
- issue_group = '1' / s_level = '80'
- issue_group = '1' / s_level = '100'
- issue_group = '1' / s_level = 'Late'
- issue_group = '2/3 ' / s_level = '80'
- issue_group = '2/3 ' / s_level = '100'
- issue_group = '2/3 ' / s_level = 'Late'
So if one of the above combinations already exists for the current s_date/part_no, then it obviously takes the qty_filled info from the current view. If not, a new line is created, and qty_filled = 0. So I'm trying to get it to look like this:
I've only shown 1 part, with a couple dates, just to get the point across. There are 10k+ parts within the table and there will never be more than 1 part/date combo for each of the 6 issue_group/s_level combos.

Answer 1

The idea is to generate the rows using CROSS JOIN and then bring in the extra information with a LEFT JOIN. In Oracle syntax, this looks like:
WITH v as (
SELECT v.*
FROM current_view v
WHERE part_no = 'xxxxx' AND
s_date IN ('201802', '201803')
)
SELECT d.s_date, ig.part_no, ig.issue_group, l.s_level,
COALESCE(v.qty_filled, 0) as qty_filled
FROM (SELECT DISTINCT s_date FROM v) d CROSS JOIN
(SELECT DISTINCT part_no, ISSUE_GROUP FROM v) ig CROSS JOIN
(SELECT '80' as s_level FROM DUAL UNION ALL
SELECT '100' FROM DUAL UNION ALL
SELECT 'LATE' FROM DUAL
) l LEFT JOIN
v
ON v.s_date = d.s_date AND v.part_no = ig.part_no AND
v.issue_group = ig.issue_group AND v.s_level = l.s_level
ORDER BY s_date, part_no, issue_group,
(CASE s_level WHEN '80' THEN 1 WHEN '100' THEN 2 WHEN 'Late' THEN 3 END)

Answer 2

One solution could be to generate a cartesian product of all expected rows using a cartesian product between the (fixed) list of values, and then LEFT JOIN it with current_view.
The following query guarantees that you will get a record for each given s_date/part_no/issue_group/s_level tuple. If no record matches in current_view, the query will display a 0 quantity.
SELECT
sd.s_date,
pn.part_no,
ig.issue_group,
sl.s_level,
COALESCE(cv.qty_filled, 0) qty_filled
FROM
(SELECT '201802' AS s_date UNION SELECT '201803') AS sd
CROSS JOIN (SELECT 'xxxxx' AS part_no) AS pn
CROSS JOIN (SELECT '1' AS issue_group UNION SELECT '2') AS ig
CROSS JOIN (SELECT '80' AS s_level UNION SELECT '100' UNION SELECT 'Late') AS sl
LEFT JOIN current_view cv
ON cv.s_date = sd.s_date
AND cv.part_no = pn.part_no
AND cv.issue_group = ig.issue_group
AND cv.s_level = ig.s_level
ORDER BY
sd.s_date,
pn.part_no,
ig.issue_group,
DECODE(sl.s_level, '80', 1, '100', 2, 'Late', 3)
NB : you did not tag your RDBMS. This should work on most of them, excepted Oracle, where you need to add FROM DUAL to each select in the queries that list the allowed values, like :
(SELECT '201802' AS s_date FROM DUAL UNION SELECT '201803' FROM DUAL) AS sd