tsql select with all variations of joins - sql

Question

For an export I have to select all stats for all years and groups, even if the combination has no amount to export.
Here an example and expected result:
DECLARE #years TABLE (yr INT)
INSERT #years VALUES (2020),(2021),(2022)
DECLARE #grps TABLE (grp INT)
INSERT #grps VALUES (1),(2),(3)
DECLARE #stats TABLE (item INT, yr INT, grp INT, amount INT)
INSERT #stats VALUES
(1,2021,1,344)
,(1,2021,2,34)
,(1,2021,3,44)
,(1,2020,1,249)
,(1,2020,3,70)
,(2,2021,1,850)
,(2,2021,2,1260)
,(2,2020,1,799)
/* EXPECTED RESULT */
/*
|item|year|grp |amout|
|1 |2020|1 | 249 |
|1 |2020|2 | 0 |
|1 |2020|3 | 70 |
|1 |2021|1 | 344 |
|1 |2021|2 | 34 |
|1 |2021|3 | 44 |
|1 |2022|1 | 0 |
|1 |2022|2 | 0 |
|1 |2022|3 | 0 |
|2 |2020|1 | 799 |
|2 |2020|2 | 0 |
|2 |2020|3 | 0 |
|2 |2021|1 | 850 |
|2 |2021|2 |1260 |
|2 |2021|3 | 0 |
|2 |2022|1 | 0 |
|2 |2022|2 | 0 |
|2 |2022|3 | 0 |
*/
I get id done with this query:
SELECT item.item
,yr.yr
,grp.grp
,ISNULL(st.amount,0) [amount]
FROM (SELECT DISTINCT item FROM #stats) item
CROSS APPLY (SELECT yr FROM #years) yr
CROSS APPLY (SELECT grp FROM #grps) grp
LEFT JOIN #stats st
ON st.item = item.item
AND st.yr = yr.yr
AND st.grp = grp.grp
ORDER BY 1,2,3
Is there no simpler solution to this?

Answer 1

It's debatable if it's a simpler solution.
But you can cross join in a CTE to get all expected combos.
Then left join the CTE to the existing data.
DECLARE #years TABLE (yr INT);
INSERT #years VALUES (2020),(2021),(2022);
DECLARE #grps TABLE (grp INT);
INSERT #grps VALUES (1),(2),(3);
DECLARE #stats TABLE (item INT, yr INT, grp INT, amount INT)
INSERT #stats VALUES
(1,2021,1,344)
,(1,2021,2,34)
,(1,2021,3,44)
,(1,2020,1,249)
,(1,2020,3,70)
,(2,2021,1,850)
,(2,2021,2,1260)
,(2,2020,1,799);
;WITH CTE_YEARS AS (
SELECT DISTINCT yr FROM #years
)
, CTE_GROUPS AS (
SELECT DISTINCT grp FROM #grps
)
, CTE_ITEMS AS (
SELECT DISTINCT item FROM #stats
)
, CTE_ALL_YEAR_GROUP_ITEMS AS (
SELECT y.yr, g.grp, i.item
FROM CTE_YEARS y
CROSS JOIN CTE_GROUPS g
CROSS JOIN CTE_ITEMS i
)
SELECT
cte.item
, cte.yr
, cte.grp
, ISNULL(stat.amount, 0) AS amount
FROM CTE_ALL_YEAR_GROUP_ITEMS cte
LEFT JOIN #stats stat
ON stat.item = cte.item
AND stat.yr = cte.yr
AND stat.grp = cte.grp
ORDER BY 1,2,3
item
yr
grp
amount
1
2020
1
249
1
2020
2
0
1
2020
3
70
1
2021
1
344
1
2021
2
34
1
2021
3
44
1
2022
1
0
1
2022
2
0
1
2022
3
0
2
2020
1
799
2
2020
2
0
2
2020
3
0
2
2021
1
850
2
2021
2
1260
2
2021
3
0
2
2022
1
0
2
2022
2
0
2
2022
3
0
Test on db<>fiddle here