SQL Server - select every combination - sql

Question

We have two tables below, I am trying to write a query that will select EVERY Purchase for EVERY person on the team. For example, it should show PersonA being associated to PurchaseID 1 and 2 because they are on the same Team as TeamA.
Is this possible? I thought a cross join would work but it seemed to bring back too many columns. I am running SQL Server.
Thank you
Purchases
| PurchaseID | PersonID |
|------------ |---------- |
| 1 | TeamA |
| 2 | TeamA |
| 3 | PersonA |
| 4 | PersonB |
| 5 | TeamB |
Teams
| TeamID | PersonID |
|-------- |---------- |
| 1 | PersonA |
| 1 | TeamA |
| 1 | PersonC |
| 2 | PersonB |
| 2 | TeamB |
Expected results (when filtered on PurchaseID 1):
| PurchaseID | PersonID |
|------------ |---------- |
| 1 | TeamA |
| 1 | PersonA |
| 1 | PersonC |

Answer 1

Your data structure is a little odd, but I think I understand what you want.
If PersonA made a purchase, and PersonA is on TeamA, then everyone on TeamA should be shown as being associated with the purchase, right? Like "I bought these doughnuts for my team, so everyone on my team gets a doughnut".
What you're going to want is to join Purchase to Team on PersonID, as you probably guessed. But then use a CROSS APPLY function, which is in inline table value function, to return all the people on the same team as the person in the "current row".
I used two common table expressions to represent your tables so I could run it. You'll just want the SELECT part:
with Purchases as (
select 1 as PurchaseID, 'TeamA' as PersonID
union select 2 as PurchaseID, 'TeamA' as PersonID
union select 3 as PurchaseID, 'PersonA' as PersonID
union select 4 as PurchaseID, 'PersonB' as PersonID
union select 5 as PurchaseID, 'TeamB' as PersonID
)
, Teams as (
select 1 as TeamID, 'PersonA' as PersonID
union select 1 as TeamID, 'TeamA' as PersonID
union select 1 as TeamID, 'PersonC' as PersonID
union select 2 as TeamID, 'PersonB' as PersonID
union select 2 as TeamID, 'TeamB' as PersonID
)
select Purchases.PurchaseID
, EveryTeamMember.PersonID
from Purchases
join Teams
on Teams.PersonID = Purchases.PersonID
cross apply (
select PersonID
from Teams InnerTable
where InnerTable.TeamID = Teams.TeamID
) as EveryTeamMember
where Purchases.PurchaseID = 1

Answer 2

If you are looking ti get all Team persons when the PersonID starts with Team then i think you should do a CROSS APPLY over all PersonID who starts with Team and UNION (NOT UNION ALL) Single Person purchases:
DECLARE #Purchases TABLE (
PurchaseID INT,
PersonID Varchar(50)
)
INSERT INTO #Purchases(PersonID,PurchaseID) VALUES ('TeamA', 1);
INSERT INTO #Purchases(PersonID,PurchaseID) VALUES ('TeamA', 2);
INSERT INTO #Purchases(PersonID,PurchaseID) VALUES ('PersonA', 3);
INSERT INTO #Purchases(PersonID,PurchaseID) VALUES ('PersonB', 4);
INSERT INTO #Purchases(PersonID,PurchaseID) VALUES ('TeamB', 5);
DECLARE #Teams TABLE (
TeamID INT,
PersonID Varchar(50)
)
INSERT INTO #Teams(PersonID,TeamID) VALUES ('PersonA', 1);
INSERT INTO #Teams(PersonID,TeamID) VALUES ('TeamA', 1);
INSERT INTO #Teams(PersonID,TeamID) VALUES ('PersonC', 1);
INSERT INTO #Teams(PersonID,TeamID) VALUES ('PersonB', 2);
INSERT INTO #Teams(PersonID,TeamID) VALUES ('TeamB', 2);
SELECT T1.PurchaseID,TeamPersons.PersonID
FROM #Purchases T1
INNER JOIN #Teams T2
ON T2.PersonID = T1.PersonID AND T1.PersonID LIKE'Team%'
CROSS APPLY (
SELECT PersonID
FROM #Teams T3
WHERE T3.TeamID = T2.TeamID
) AS TeamPersons
UNION
SELECT T1.PurchaseID
, T1.PersonID
FROM #Purchases T1
WHERE T1.PersonID NOT LIKE 'Team%'
Result