Tech Off - Should be simple SQL, but I'm missing something

qwert231 — Fri, 12 Dec 2008 17:45:53 GMT

We have two tables, Districts and DayAllotment
Districts is:
DistrictID int
Description varchar(25)

DayAllotment is:
AllotmentID
DistrictID
DaysAllotted
HalfYear
Type
Year

My Data in Day Allotment is something like this:
1    1012    23    First    Fish    2008
2    1012    22    Second    Fish    2008
3    1012    15    First    Boat    2008
4    1012    14    Second    Boat    2008
5    2012    23    First    Boat    2008
6    2012    22    Second    Fish    2008
7    2012    14    Second    Boat    2008

So, let's say I want a result set that looks for All Fish allotments for 2008. I want a result set that looks like this:
DistrictID    First    Second
1012    23    22
1013    NULL    22

I tried something like this:

SELECT dist.DistrictID, fDays.DaysAllotted AS 'Jan.-Jun.', sDays.DaysAllotted AS 'Jul.-Dec.'
FROM dbo.law_Districts dist
    LEFT JOIN law_DeputyDaysAllotment fDays ON dist.DistrictID = fDays.DistrictID
    LEFT JOIN law_DeputyDaysAllotment sDays ON dist.DistrictID = sDays.DistrictID
WHERE ((fDays.HalfYearWindow = 'First' AND fDays.Year = @Year AND fDays.Type = @Type) OR (fDays.HalfYearWindow IS NULL))
    OR ((sDays.HalfYearWindow = 'Second' AND sDays.Year = @Year AND sDays.Type = @Type) OR (sDays.HalfYearWindow IS NULL))ORDER BY dist.DistrictID

But get the same results in both columns.

I've tried some other ways of joining, but have gotten results where some districts were dropped. I won't always know which side will have the NULL values.

I'm sure there are samples out there but I'm not sure what to search for. Would this be a cross join table?

Tech Off - Should be simple SQL, but I'm missing something

dpratt71 — Fri, 12 Dec 2008 22:08:44 GMT

Definitely not a cross join. You want a "full outer join" (includes rows from both tables even when they don't match). Here's the basic idea (minus the "where" clause):

SELECT
   COALESCE(fDays.DistrictID, sDays.DistrictID) DistrictID
   , fDays.DaysAllotted AS 'Jan.-Jun.'
   , sDays.DaysAllotted AS 'Jul.-Dec.'
FROM
   law_DeputyDaysAllotment fDays
   FULL OUTER JOIN law_DeputyDaysAllotment sDays ON
   fDays.DistrictID = sDays.DistrictID
   AND fDays.Year = sDays.Year
   AND fDays.Type = sDays.Type

I did this by hand and didn't check it, so there may be one or two syntax errors lurking in there.

Channel 9 Forums - Tech Off - Should be simple SQL, but I'm missing something

Tech Off - Should be simple SQL, but I'm missing something

Tech Off - Should be simple SQL, but I'm missing something