Display All Rows In Left Outer Join (was Would Be So Grateful For Sql Help)

This is what I want my results to look like

invoice wbs1 wbs2 amount
8060 000-333 500 0
8060 000-333 100 0
8060 000-333 140 0
8060 000-333 150 4335
8060 000-333 160 0
8267 000-333 500 0
8267 000-333 100 20500
8267 000-333 140 547.50
8267 000-333 150 2000
8267 000-333 160 5000


This is what I have so far:

SELECT PR.WBS1, PR.WBS2, ledgerar.invoice, SUM(CASE WHEN ledgerar.transtype = 'in' AND ledgerar.period = '200405' THEN ledgerar.amount * - 1 END) AS amount
FROM PR LEFT OUTER JOIN
LedgerAR ON LedgerAR.WBS1 = PR.WBS1 AND LedgerAR.WBS2 = PR.WBS2 AND LedgerAR.WBS3 = PR.WBS3
WHERE (LedgerAR.wbs1 = '001-333') AND ledgerar.period = '200405'
GROUP BY pr.wbs1, pr.wbs2, ledgerar.invoice


the above query gives me the following results:

invoice wbs1 wbs2 amount
8060 000-333 100 0
8060 000-333 140 0
8060 000-333 160 4335
8267 000-333 100 1320
8267 000-333 140 20912.5
8267 000-333 150 8363
8267 000-333 160 2650


But I don't know how to get the query to display all of wbs2 whether it is null or not. So, for each invoice number there should be five records according to the wbs2 codes (500, 100, 140, 150, 160)

Does anyone know how to do this?

Thanks,
Laura