Inserting missing rows with a join - sql

Question

I have a SQL script that returns this derived table.
MM/YYYY Cat Score
01/2012 Test1 17
02/2012 Test1 19
04/2012 Test1 15
05/2012 Test1 16
07/2012 Test1 14
08/2012 Test1 15
09/2012 Test1 15
12/2012 Test1 11
01/2013 Test2 10
02/2013 Test2 15
03/2013 Test2 13
05/2013 Test2 18
06/2013 Test2 14
08/2013 Test2 15
09/2013 Test2 14
12/2013 Test2 10
As you can see, I am missing some MM/YYYYs (03/2012, 06/2012, 11/2012, etc).
I would like to fill in the missing MM/YYYYs with the Cat & a 0 (zero) form the score.
I have tried to join a table that contains the all MM/YYYY for the ranges the query will be run, but this only returns the missing rows for the first occurrence, it does not repeat for each Cat (should have known that).
So my question is this, can I do this using a join or will I have to do this in a temp table, and then output the data.
AHIGA,
LarryR…

Answer 1

You need to cross join your categories and a list of all dates in the range. Since you have posted no table structures I'll have to guess at your structure slightly, but assuming you have a calendar table you can use something like this:
SELECT calendar.Date,
Category.Cat,
Score = ISNULL(Scores.Score, 0)
FROM Calendar
CROSS JOIN Catogory
LEFT JOIN Scores
ON Scores.Cat = Category.Cat
AND Scores.Date = Calendar.Date
WHERE Calendar.DayOfMonth = 1;
If you do not have a calendar table you can generate a list of dates using the system table Master..spt_values:
SELECT Date = DATEADD(MONTH, Number, '20120101')
FROM Master..spt_values
WHERE Type = 'P';
Where the hardcoded date '20120101' is the first date in your range.
ADDENDUM
If you need to actually insert the missing rows, rather than just have a query that fills in the blanks you can use this:
INSERT Scores (Date, Cat, Score)
SELECT calendar.Date,
Category.Cat,
Score = 0
FROM Calendar
CROSS JOIN Catogory
WHERE Calendar.DayOfMonth = 1
AND NOT EXISTS
( SELECT 1
FROM Scores
WHERE Scores.Cat = Category.Cat
AND Scores.Date = Calendar.Date
)
Although, in my opinion if you have a query that fills in the blanks inserting the data is a bit of a waste of time.

Answer 2

To get what you want, start with a driver table and then use left outer join. The result is something like this:
select driver.cat, driver.MMYYYY, coalesce(t.score, 0) as score
from (select cat, MMYYYY
from (select distinct cat from t) c cross join
themonths -- use where to get a date range
) driver left outer join
t
on t.cat = driver.cat and t.MMMYYYY = driver.MMYYYY

Answer 3

Try this one -
DECLARE #temp TABLE (FDOM DATETIME, Cat NVARCHAR(50), Score INT)
INSERT INTO #temp (FDOM, Cat, Score)
VALUES
('20120101', 'Test1', 17),('20120201', 'Test1', 19),
('20120401', 'Test1', 15),('20120501', 'Test1', 16),
('20120701', 'Test1', 14),('20120801', 'Test1', 15),
('20120901', 'Test1', 15),('20121001', 'Test1', 13),
('20121201', 'Test1', 11),('20130101', 'Test1', 10),
('20130201', 'Test1', 15),('20130301', 'Test1', 13),
('20130501', 'Test1', 18),('20130601', 'Test1', 14),
('20130801', 'Test1', 15),('20130901', 'Test1', 14),
('20131201', 'Test1', 10),('20120601', 'Test2', 10)
;WITH enum AS
(
SELECT Cat, StartDate = MIN(FDOM), EndDate = MAX(FDOM)
FROM #temp
GROUP BY Cat
UNION ALL
SELECT Cat, DATEADD(MONTH, 1, StartDate), EndDate
FROM enum
WHERE StartDate < EndDate
)
SELECT e.StartDate, t.Cat, Score = ISNULL(t.Score, 0)
FROM enum e
LEFT JOIN #temp t ON e.StartDate = t.FDOM AND e.Cat = t.Cat
ORDER BY e.StartDate, t.Cat

Answer 4

Do a left join from "complete table" to "incomplete table" and set a where statement to check the date column of the "incomplete" table. So you will only get the missing results in your select query. After that, just set a "insert into tablename" before.
In the first run it will find two rows, that aren't already in the incomplete table. So it will be inserted by the insert into statement, two rows affected. In a second run the result in the select statement has 0 rows, so nothing happens. Zero rows affected :-)
Sample: http://sqlfiddle.com/#!2/895fe/6
(Just mark the select statement; the insert into statement isn't required to just see, how the join works)
Insert Into supportContacts
Select * FROM
(
Select
'01/2012' as DDate, 'Test1' as Cat, 17 as Score
UNION
Select
'02/2012' as DDate, 'Test1' as Cat, 17 as Score
UNION
Select
'03/2012' as DDate, 'Test1' as Cat, 17 as Score
UNION
Select
'04/2012' as DDate, 'Test1' as Cat, 17 as Score
UNION
Select
'05/2012' as DDate, 'Test1' as Cat, 17 as Score
) CompleteTable
LEFT JOIN
(
Select
'01/2012' as DDate, 'Test1' as Cat, 17 as Score
UNION
Select
'02/2012' as DDate, 'Test1' as Cat, 17 as Score
UNION
Select
'03/2012' as DDate, 'Test1' as Cat, 17 as Score
) InCompleteTable
ON CompleteTable.DDate = IncompleteTable.DDate
WHERE IncompleteTable.DDate is null