Select N rows in aggregate functions SQL Server - sql

Question

I have a table that looks like this:
+--------+----------+--------+------------+-------+
| ID | CHANNEL | VENDOR | num_PERIOD | SALES |
+--------+----------+--------+------------+-------+
| 000001 | Business | Shop | 1 | 40 |
| 000001 | Business | Shop | 2 | 60 |
| 000001 | Business | Shop | 3 | NULL |
+--------+----------+--------+------------+-------+
With many combinations of ID, CHANNEL and VENDOR, and sales records for each of them over time (num_PERIOD).
The idea is to obtain a new column which returns the number of NULLS in SALES column, but in the first 111 registers according to num_PERIOD column.
I have been trying something like this:
SELECT ID,
CHANNEL,
VENDOR,
sum(CASE
WHEN SALES IS NULL THEN 1
ELSE 0
END) OVER (PARTITION BY ID,
CHANNEL,
VENDOR
ORDER BY num_PERIOD ROWS BETWEEN UNBOUNDED PRECEDING AND 111 FOLLOWING) AS NULL_SALES_SET
FROM TABLE
GROUP BY ID,
CHANNEL,
VENDOR
But I'm not obtaining what I'm looking for.
So to obtain a table simillar to:
+--------+--------------+--------+----------------+
| ID | CHANNEL | VENDOR | NULL_SALES_SET |
+--------+--------------+--------+----------------+
| 000001 | Business | Shop | 1 |
| 000002 | Business | Market | 0 |
| 000002 | Non Business | Shop | 3 |
+--------+--------------+--------+----------------+
The difficulty comes when selecting these first 111 rows per ID, CHANNEL AND VENDOR ordered by num_PERIOD.

Answer 1

Use a CTE (Common Table Expression) with the ROW_NUMBER windowed function and you should be set:
;WITH MyCTE AS
(
SELECT
id,
channel,
vendor,
sales,
ROW_NUMBER() OVER (PARTITION BY id, channel, vendor ORDER BY num_period) AS row_num
FROM
MyTable
)
SELECT
id,
channel,
vendor,
SUM(CASE WHEN sales IS NULL THEN 1 ELSE 0 END) AS null_sales_set
FROM
MyCTE
WHERE
row_num <= 111
GROUP BY
id, channel, vendor

Answer 2

Do you have to use the windowing function?
SELECT ID
, CHANNEL
, VENDOR
, NULL_SALES_SET = SUM(CASE WHEN SALES IS NULL THEN 1 ELSE 0 END)
FROM Table
WHERE num_PERIOD <= 111
GROUP BY ID, CHANNEL, VENDOR
Or are you looking for the first 111 num_PERIOD values allowing for gaps in the num_PERIOD column?
SELECT t.ID
, t.CHANNEL
, t.VENDOR
, NULL_SALES_SET = SUM(CASE WHEN t.SALES IS NULL THEN 1 ELSE 0 END)
FROM Table t
INNER JOIN ( SELECT i.ID
, i.CHANNEL
, i.VENDOR
, i.num_PERIOD
, rowNum = ROW_NUMBER(PARTITION BY i.ID, i.CHANNEL, i.VENDOR ORDER BY i.num_PERIOD)
FROM Table i ) l
ON t.ID = l.ID
AND t.CHANNEL = l.CHANNEL
AND t.VENDOR = l.VENDOR
AND t.num_PERIOD = l.num_PERIOD
WHERE l.rowNum <= 111
GROUP BY ID, CHANNEL, VENDOR
Edit: Not sure how I overlooked it, but it is necessary to JOIN on the num_PERIOD column.
Edit: Add the number of distinct num_PERIOD per ID, Channel, Vendor without affecting the NULL_SALES_SET
SELECT t.ID
, t.CHANNEL
, t.VENDOR
-- Counts the NULL Sales when the num_PERIOD is in the
-- first 111 num_PERIODs
, NULL_SALES_SET = SUM(CASE WHEN l.rowNum IS NOT NULL AND t.SALES IS NULL
THEN 1
ELSE 0 END)
-- Counts the distinct num_PERIOD values
, PERIOD_COUNT = COUNT(DISTINCT t.num_PERIOD)
FROM Table t
LEFT OUTER JOIN ( SELECT i.ID
, i.CHANNEL
, i.VENDOR
, i.num_PERIOD
, rowNum = ROW_NUMBER(PARTITION BY i.ID,
i.CHANNEL,
i.VENDOR
ORDER BY i.num_PERIOD)
FROM Table i ) l
ON t.ID = l.ID
AND t.CHANNEL = l.CHANNEL
AND t.VENDOR = l.VENDOR
AND t.num_PERIOD = l.num_PERIOD
AND l.rowNum <= 111
GROUP BY ID, CHANNEL, VENDOR