Question

Given the following tables:

table objects

id    Name   rating
1     Megan      9
2     Irina     10
3     Vanessa    7
4     Samantha   9
5     Roxanne    1
6     Sonia      8

swap table

id   swap_proposalid   counterpartyid
1                 4                2
2                 3                2

Everyone wants the ten. I would like to make a list for Irina of possible swaps where id 4 and 3 don’t appear because the propositions are already there.

output1

id   Name    rating
1     Megan      9
5     Roxanne    1
6     Sonia      8

Thanks

Answer 1

This works

SELECT mt2.ID, mt2.Name, mt2.Rating
FROM [MyTable] mt2  -- Other Candidates
   , [MyTable] mt1 -- Candidate / Subject (Irina)
WHERE mt2.ID NOT IN 
  (
    SELECT st.swap_proposalid
    FROM SwapTable st
    WHERE
      st.counterpartyid = mt1.ID
  )
AND mt1.ID <> mt2.ID -- Don't match Irina with Irina
AND mt1.Name = 'Irina' -- Find other swaps for Irina

— Test Data

CREATE TABLE MyTable
(
  ID INT, 
  Name VARCHAR(100),
  Rating INT
)
GO
CREATE TABLE SwapTable
(
  ID INT,
  swap_proposalid INT,
  counterpartyid INT
)
GO

INSERT INTO MyTable VALUES(1     ,'Megan',       9)
INSERT INTO MyTable VALUES(2     ,'Irina',      10)
INSERT INTO MyTable VALUES(3     ,'Vanessa',    7)
INSERT INTO MyTable VALUES(4     ,'Samantha',   9)
INSERT INTO MyTable VALUES(5     ,'Roxanne',    1)
INSERT INTO MyTable VALUES(6     ,'Sonia',      8)

INSERT INTO SwapTable(ID, swap_proposalid, counterpartyid)
VALUES (1, 4, 2)
INSERT INTO SwapTable(ID, swap_proposalid, counterpartyid)
VALUES (1, 3, 2)