SQL Query to Show When Golfer Not Attached to an Event/Year - sql

Question

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

Answer 1

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;

Answer 2

Try this query:
SELECT tg.intGolferID, strLastName, tey.intEventYearID, tey.intEventYear
FROM TGolfers tg, TEventYears tey
WHERE tg.intGolferID NOT IN (
SELECT DISTINCT tgey.intGolferID
FROM TGolferEventYears tgey
WHERE tgey.intEventYearID = tey.intEventYearID
)
Explanation
Since you are trying to get combinations of data that is not in TGolferEventYears, you cannot use it in your outer-most SELECT as any of its columns would be NULL. Therefore, you need to SELECT FROM the tables that are the sources of that data, and going through each joined record, filter out the combinations that are in TGolferEventYears.
Main query
Select the data you need:
SELECT tg.intGolferID, strLastName, tey.intEventYearID, tey.intEventYear
...from TGolfers, cross join with TEventYears:
FROM TGolfers tg, TEventYears tey
...where the golfer ID does not exist in the following collection:
WHERE tg.intGolferID NOT IN ( ... )
Subquery
Select unique golfer IDs:
SELECT DISTINCT tgey.intGolferID
...from TGolferEventYears:
FROM TGolferEventYears tgey
...where the year is the current year of the outer query:
WHERE tgey.intEventYearID = tey.intEventYearID
Result
+-------------+-------------+----------------+--------------+
| intGolferID | strLastName | intEventYearID | intEventYear |
+-------------+-------------+----------------+--------------+
| 1 | Goldstein | 1 | 2015 |
| 1 | Goldstein | 3 | 2017 |
| 2 | Everett | 3 | 2017 |
+-------------+-------------+----------------+--------------+