How to insert "empty" row extracting a month list? - sql-server

Question

I've this sp, which return a list of data, for each "month" (i.e. each row is a month). Somethings like that:
SELECT
*,
(CAST(t1.NumActivities AS DECIMAL) / t1.NumVisits) * 100 AS PercAccepted,
(CAST(t1.Accepted AS DECIMAL) / t1.Estimated) * 100 AS PercValue
FROM
(SELECT
MONTH(DateVisit) AS Month,
COUNT(*) AS NumVisits,
SUM(CASE WHEN DateActivity is not null THEN 1 ELSE 0 END) AS NumActivities,
SUM(Estimate) AS Estimated,
SUM(CASE WHEN DateActivity is not null THEN Estimate ELSE 0 END) AS Accepted
FROM [dbo].[Activities]
WHERE
DateVisit IS NOT NULL
AND (#year IS NULL OR YEAR(DateVisit) = #year)
AND (#clinicID IS NULL OR ClinicID = #clinicID)
GROUP BY MONTH(DateVisit)) t1
This is a result:
Month NumVisits NumActivities Estimated Accepted PercAccepted PercValue
1 5 1 13770.00 2520.00 20.00000000000 18.30065359477124
2 2 2 7900.00 7900.00 100.00000000000 100.00000000000000
3 1 0 2730.00 0.00 0.00000000000 0.00000000000000
8 1 1 3000.00 3000.00 100.00000000000 100.00000000000000
But as you can see, I could "miss" some Month (for example, here April "4" is missed).
Is it possible to insert, for the missing month/row, an empty (0) record? Such as:
Month NumVisits NumActivities Estimated Accepted PercAccepted PercValue
1 5 1 13770.00 2520.00 20.00000000000 18.30065359477124
2 2 2 7900.00 7900.00 100.00000000000 100.00000000000000
3 1 0 2730.00 0.00 0.00000000000 0.00000000000000
4 0 0 0 0 0 0
...

Answer 1

Here is a example with sample data:
CREATE TABLE #Report
(
Id INT,
Name nvarchar(max),
Percentage float
)
INSERT INTO #Report VALUES (1,'ONE',2.01)
INSERT INTO #Report VALUES (2,'TWO',3.01)
INSERT INTO #Report VALUES (5,'Five',5.01)
;WITH months(Month) AS
(
SELECT 1
UNION ALL
SELECT Month+1
FROM months
WHERE Month < 12
)
SELECT *
INTO #AllMonthsNumber
from months;
Your select query:
The left join will gives you the NULL for other months so just use ISNULL('ColumnName','String_to_replace')
\/\/\/\/
SELECT Month, ISNULL(Name,0), ISNULL(Percentage,0)
FROM AllMonthsNumber A
LEFT JOIN #Report B
ON A.Month = B.Id
EDIT:
Yes you can do it without creating AllMonthNumber Table:
You can use master..spt_values (found here) system table which contains the numbers so just with some where condition.
SELECT Number as Month, ISNULL(B.Name,0), ISNULL(Percentage,0)
FROM master..spt_values A
LEFT JOIN #Report B ON A.Number = B.Id
WHERE Type = 'P' AND number BETWEEN 1 AND 12