How to get the value of a different ID that is acquired during the SELECT statement?-CodePudding

I have created an entity tblPerson and from this entity I need to get the bGroup of t.adminID and the bGroup from the d.personID. I have tried the below query but it's not returning anything.

SELECT t.adminID, p.firstName, p.lastName, t.transID, t.transDate, t.donationID, p.bGroup, b.bankName, d.personID AS 'Donor ID', 'Donor BGroup'
FROM tblTrans t
JOIN tblAdmin a ON t.adminID = a.adminID
JOIN tblPerson p ON a.personID = p.personID
JOIN tblDonation d ON t.donationID = d.donationID
JOIN tblBank b ON d.bankID = b.bankID
WHERE 'Donor BGroup' IN
    (SELECT p.bGroup
    FROM tblPerson p
    JOIN tblDonation d ON p.personID = d.personID
    JOIN tblTrans t ON d.donationID = t.donationID);

When I execute the subquery, it gives me the bGroup of the d.personID, what do you think is going on, and maybe any alternatives, please?

Sample Data

INSERT INTO tblPerson (personID, firstName, lastName, bGroup)
VALUES ('1A', 'John', 'Doe', 'XY'),
('2A', 'Joe', 'Bishop', 'AB'),
('1B', 'Elly', 'James', 'OP'),
('2B', 'Andre', 'Butch', 'XY'),
('3A', 'Amy', 'Gree', 'AB'),
('3B', 'Alfred', 'Black', 'OP'),
('4C', 'James', 'Brown', 'XY');
    
INSERT INTO tblAdmin (adminID, personID, description)
VALUES (1, '1A', 'Whatever.'),
(2, '1B', ''),
(3, '4C', 'Anything.'),
(4, '1A', '');

INSERT INTO tblDonation (donationID, bankID, personID, donationDate)
VALUES (1, 1, '3B', '2018-12-27'),
(2, 1, '2A', '2022-12-28'),
(3, 2, '3A', '2022-03-23'),
(4, 2, '4C', '2022-06-19'),
(5, 3, '1B', '2022-08-19'),
(6, 3, '2B', '2022-08-08'),
(7, 3, '3B', '2022-07-20'),
(8, 2, '4C', '2022-11-26'),
(9, 1, '3B', '2022-11-26'),
(10, 2, '2A', '2022-01-16');

INSERT INTO tblBank (bankID, bankName)
VALUES (1, 'Bank 1'),
(2, 'Bank 2'),
(3, 'Bank 3');

INSERT INTO tblTrans (transID, transDate, donationID, adminID)
VALUES (1, '2022-12-31', 1, 1),
(2, '2022-01-01', 2, 1),
(3, '2022-05-23', 3, 2),
(4, '2022-05-23', 4, 2),
(5, '2022-07-09', 5, 3),
(6, '2022-08-20', 6 4),
(7, '2022-12-27', 7,4);

Sample ERD Diagram

Expected Output Example: 1, John, Doe, 1, 2022-12-31, 1, XY, Bank 1, 3B, OP.

CodePudding user response：

Your WHERE 'Donor BGroup' IN (SELECT...) clause evaluates to WHERE false, because you don't have any rows with that value in tblPerson.bGroup. So, your SELECT statement's result set is empty.

It's hard to puzzle out your requirement from your question.

CodePudding user response：

I managed to find the solution. Since I needed to call the same table twice with different IDs I had to create two aliases and JOIN the table twice, like so:

SELECT t.adminID, person.firstName, person.lastName, t.transID, t.transDate, t.donationID, person.bGroup, b.bankName, donor.personID AS 'Donor ID', donor.bGroup AS 'Donor BGroup'
FROM tblTrans t
JOIN tblAdmin a ON t.adminID = a.adminID
JOIN tblPerson person ON a.personID = person.personID
JOIN tblDonation d ON t.donationID = d.donationID
JOIN tblPerson donor ON 
JOIN tblBank b ON d.bankID = b.bankID;