Left connections from top left join

Question

I am not sure how to accomplish what I am trying to do. Here is a simplified version:

CREATE TABLE PO (
POID int,
PONumber varchar(20)
)

INSERT INTO PO
(POID, PONumber)
VALUES (1, '2520001')

CREATE TABLE WSR (
WSRID int,
POID int,
WSRNumber varchar(1)
)

INSERT INTO WSR
(WSRID, POID, WSRNumber)
VALUES (1, 1, '1')

INSERT INTO WSR
(WSRID, POID, WSRNumber)
VALUES (2, 1, '2')

CREATE TABLE Invoice(
InvoiceID int,
POID int,
InvoiceNumber varchar(20)
)

INSERT INTO Invoice
(InvoiceID, POID, InvoiceNumber)
VALUES (1, 1, '11111111')

INSERT INTO Invoice
(InvoiceID, POID, InvoiceNumber)
VALUES (2, 1, '11111111 C010001')

INSERT INTO Invoice
(InvoiceID, POID, InvoiceNumber)
VALUES (3, 1, '11111111 H010001')

INSERT INTO Invoice
(InvoiceID, POID, InvoiceNumber)
VALUES (4, 1, '11111111 Q010001')

INSERT INTO Invoice
(InvoiceID, POID, InvoiceNumber)
VALUES (5, 1, '22222222')

CREATE TABLE InvoiceMatch(
POID int,
InvoiceID int,
WSRID int)

INSERT INTO InvoiceMatch
(POID, InvoiceID, WSRID)
VALUES (1, 1, 1)

INSERT INTO InvoiceMatch
(POID, InvoiceID, WSRID)
VALUES (1, 5, 2)

From this data I want to get this result:

PONumber, WSRNumber, InvoiceNumber
2520001   1          11111111
2520001   NULL       11111111 C010001
2520001   NULL       11111111 H010001
2520001   NULL       11111111 Q010001
2520001   2          22222222

I am currently using the following query:

SELECT DISTINCT p.POID, p.PONumber, w.WSRNumber, i.InvoiceNumber
FROM PO p
LEFT OUTER JOIN InvoiceMatch im ON im.POID = p.POID
LEFT OUTER JOIN WSR w ON w.POID = im.POID
LEFT OUTER JOIN Invoice i ON i.POID = im.POID
WHERE p.PONumber = '2520001'

but this is wrong. All WSRs are tied to each account. Help?

Answer 1

Try the following:

SELECT  DISTINCT p.POID
    ,p.PONumber
    ,w.WSRNumber
    ,i.InvoiceNumber
FROM PO p INNER JOIN Invoice i 
  ON i.POID = p.POID LEFT JOIN InvoiceMatch im 
  ON i.InvoiceID = im.InvoiceID LEFT OUTER JOIN WSR w 
  ON im.WSRID = w.WSRID
WHERE p.PONumber = '2520001'

Answer 2

I think that the order of your tables in some of yours Left Outer Joinsmay be disabled:

SELECT DISTINCT p.POID, p.PONumber, w.WSRNumber, i.InvoiceNumber
FROM PO p
LEFT OUTER JOIN InvoiceMatch im ON p.POID = im.POID
LEFT OUTER JOIN WSR w ON im.POID = w.POID
LEFT OUTER JOIN Invoice i ON m.POID = i.POID
WHERE p.PONumber = '2520001'

Or switch the connections in the previous request to Right Outer Joinsinstead of Left.