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