I'm trying to write a quick (ha!) program to organise some of my financial information. What I ideally want is a query that will return all records with financial information in them from TableA. There should be one row for each month, but in instances where there were no transactions for a month there will be no record. I get results like this:

SELECT Period,Year,TotalValue FROM TableA WHERE Year='1997'

Result:

Period Year  TotalValue
1      1997  298.16
2      1997  435.25
4      1997  338.37
8      1997  336.07
9      1997  578.97
11     1997  361.23

By joining on a table (well a View in this instance) which just contains a field Period with values from 1 to 12, I expect to get something like this:

SELECT p.Period,a.Year,a.TotalValue
FROM Periods AS p
LEFT JOIN TableA AS a ON p.Period = a.Period
WHERE Year='1997'

Result:

Period Year  TotalValue
1      1997  298.16
2      1997  435.25
3      NULL  NULL
4      1997  338.37
5      NULL  NULL
6      NULL  NULL
7      NULL  NULL
8      1997  336.07
9      1997  578.97
10     NULL  NULL
11     1997  361.23
12     NULL  NULL

What I'm actually getting though is the same result no matter how I join it (except CROSS JOIN which goes nuts, but it's really not what I wanted anyway, it was just to see if different joins are even doing anything). LEFT JOIN, RIGHT JOIN, INNER JOIN all fail to provide the NULL records I am expecting.

Is there something obvious that I'm doing wrong in the JOIN? Does it matter that I'm joining onto a View?