Showing one row for each calendar week in SQL - sql

Question

I have a SQL query which pulls unit sales by item, by week:
SELECT sls_vendor,
sls_item,
sls_units,
DATEPART(week, sls_week) AS sls_date
FROM mytable
Assume I'm looking at a 8 week period, but not every item/vendor combination has a full 8 weeks of sales. However I need my query to show a null value in that instance. So the query would return 8 rows for each item/vendor combination regardless of existence.
I tried creating a temp table which has the numbers 28 to 35 and performing a left join on the query above, but that doesn't show null values. The results are no different than running the original query alone.
I can think of how this would be done using a crosstab/pivot query, but isn't this something the join should be doing?
Edit: Updated to show my join query. Datetable just has 8 rows with 1 incremental number for each calendar week.
SELECT * FROM #datetable
LEFT JOIN
(SELECT
sls_vendor,
sls_item,
sls_units,
datepart(week,sls_week) AS sls_date
FROM mytable) AS QRY
ON temp_week = qry.sls_date

Answer 1

Your method should work just fine:
;with mytable as (
select 1 as sls_vendor, 'Test' as sls_item, 30 as sls_units, '8/7/2011' as sls_week union
select 1 as sls_vendor, 'Test' as sls_item, 30 as sls_units, '8/14/2011' as sls_week union
select 1 as sls_vendor, 'Test' as sls_item, 30 as sls_units, '8/21/2011' as sls_week
)
,datetable as (
select 28 as temp_week union
select 29 union
select 30 union
select 31 union
select 32 union
select 33 union
select 34 union
select 35
)
SELECT * FROM datetable
LEFT JOIN
(SELECT
sls_vendor,
sls_item,
sls_units,
datepart(week,sls_week) AS sls_date
FROM mytable) AS QRY
ON temp_week=qry.sls_date
Output:
temp_week sls_vendor sls_item sls_units sls_date
28 NULL NULL NULL NULL
29 NULL NULL NULL NULL
30 NULL NULL NULL NULL
31 NULL NULL NULL NULL
32 NULL NULL NULL NULL
33 1 Test 30 33
34 1 Test 30 34
35 1 Test 30 35
Edit: If you want to include all week values for every sales vendor, include a cross join with the distinct selection of vendors:
;with mytable as (
select 1 as sls_vendor, 'Test' as sls_item, 30 as sls_units, '8/7/2011' as sls_week union
select 2 as sls_vendor, 'Test' as sls_item, 30 as sls_units, '8/14/2011' as sls_week union
select 3 as sls_vendor, 'Test' as sls_item, 30 as sls_units, '8/21/2011' as sls_week
)
,datetable as (
select 28 as temp_week union
select 29 union
select 30 union
select 31 union
select 32 union
select 33 union
select 34 union
select 35
)
SELECT * FROM datetable
cross join (select distinct sls_vendor from mytable) v
LEFT JOIN
(SELECT
sls_vendor,
sls_item,
sls_units,
datepart(week,sls_week) AS sls_date
FROM mytable) AS QRY
ON temp_week=qry.sls_date and v.sls_vendor=qry.sls_vendor
Output:
temp_week sls_vendor sls_vendor sls_item sls_units sls_date
28 1 NULL NULL NULL NULL
29 1 NULL NULL NULL NULL
30 1 NULL NULL NULL NULL
31 1 NULL NULL NULL NULL
32 1 NULL NULL NULL NULL
33 1 1 Test 30 33
34 1 NULL NULL NULL NULL
35 1 NULL NULL NULL NULL
28 2 NULL NULL NULL NULL
29 2 NULL NULL NULL NULL
30 2 NULL NULL NULL NULL
31 2 NULL NULL NULL NULL
32 2 NULL NULL NULL NULL
33 2 NULL NULL NULL NULL
34 2 2 Test 30 34
35 2 NULL NULL NULL NULL
28 3 NULL NULL NULL NULL
29 3 NULL NULL NULL NULL
30 3 NULL NULL NULL NULL
31 3 NULL NULL NULL NULL
32 3 NULL NULL NULL NULL
33 3 NULL NULL NULL NULL
34 3 NULL NULL NULL NULL
35 3 3 Test 30 35

Answer 2

Does it work for you?
SELECT sls_vendor,
sls_item,
sls_units,
DATEPART(WEEK, sls_week) AS sls_date
FROM (
SELECT VALUE = 28 UNION ALL
SELECT VALUE = 29 UNION ALL
SELECT VALUE = 30 UNION ALL
SELECT VALUE = 31 UNION ALL
SELECT VALUE = 32 UNION ALL
SELECT VALUE = 33 UNION ALL
SELECT VALUE = 34 UNION ALL
SELECT VALUE = 35
) dates
LEFT JOIN mytable m
ON dates.value = DATEPART(WEEK, m.sls_week)

Answer 3

The following query works in Data.StackExchange. See here. It gets the top Post per week by score.
WITH weeksyears
AS (SELECT w.NUMBER AS week,
y.NUMBER AS year
FROM (SELECT v.NUMBER
FROM MASTER..spt_values v
WHERE TYPE = 'P'
AND v.NUMBER BETWEEN 1 AND 52) w,
(SELECT v.NUMBER
FROM MASTER..spt_values v
WHERE TYPE = 'P'
AND v.NUMBER BETWEEN 2008 AND 2012) y),
topPostPerWeek
AS (SELECT score,
Datepart(week, creationdate) week,
Datepart(YEAR, creationdate) YEAR,
Row_number() OVER (PARTITION BY Datepart(wk, creationdate),
Datepart(
YEAR,
creationdate) ORDER BY score DESC) row
FROM posts)
SELECT *
FROM weeksyears wy
LEFT JOIN topPostPerWeekt
ON wy.week = t.week
AND wy.YEAR = t.YEAR
WHERE row = 1
OR row IS NULL
ORDER BY wy.YEAR, wy.WEEK
​
Every row prior to the 38 week in 2008 is empty except for week and year. As well as the rows after the 35 week in 2011.
However if you edit the query and remove OR row IS NULL the query will act just as if it were an INNER JOIN
My guess is that there's somthing in your WHERE that's referring to the "RIGHT" table. Just add OR [rightTable.field] IS NULL and you'll be fine.