I am working on a school assignment that has downright stumped me for days. The task is to, using a view (VAvailableGolfers), populate a list box with Golfers who are not tied to a given event/year selected from a combo box. Here is the data in the tables:
The expected output on the form, then, would be:
- 2015 shows Goldstein available
- 2016 shows no one available
- 2017 shows both Goldstein and Everett available
so, in other words, where there isn’t a record in TGolferEventYears for a golfer for a particular year
I have tried left joins, full outer joins, exists, not in, not exists, etc and I cannot seem to nail down the SQL to make it happen.
Here is the VB Form and the SQL backing it. I cannot figure out what to code in the view:
“SELECT intGolferID, strLastName FROM vAvailableGolfers WHERE intEventYearID = ” & cboEvents.SelectedValue.ToString
Here is the view, which I know isn’t giving correct output:
select tg.intGolferID, strLastName, intEventYearID
from TGolferEventYears TGEY, TGolfers TG
Where tgey.intGolferID = tg.intGolferID
and intEventYearID not IN
(select intEventYearID
from TEventYears
where intEventYearID not in
(select intEventYearID
from TGolferEventYears))
Appreciate any help
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Answer
I usually approach this type of question by using a cross join
to generate all possibly combination and then a left join
/where
to filter out the ones that already exist:
select g.intGolferID, g.strLastName, ey.intEventYearID
from TEventYears ey cross join
TGolfers g left join
TGolferEventYears gey
on gey.intGolferID = g.intGolferID and
gey.intEventYearID = ey.intEventYearID
where gey.intGolferID is null;