Not sure why your LEFT JOIN didn't work but just to illustrate the idea:

--This is a list of All location groups

CREATE TABLE #LocationGroups(

LocationGroup VARCHAR(20) PRIMARY KEY

);

INSERT INTO #LocationGroups(LocationGroup)

SELECT 'AAA' UNION ALL

SELECT 'BBB' UNION ALL

SELECT 'CCC' UNION ALL

SELECT 'DDD' UNION ALL

SELECT 'EEE'

--This is your current data with some location groups missing

CREATE TABLE #ReportData(

LocationGroup VARCHAR(20)

,SomeOtherData VARCHAR(100)

);

INSERT INTO #ReportData(LocationGroup, SomeOtherData)

SELECT 'AAA', 'DataA1' UNION ALL

SELECT 'AAA', 'DataA3' UNION ALL

SELECT 'CCC', 'DataC1' UNION ALL

SELECT 'EEE', 'DataE1' UNION ALL

SELECT 'EEE', 'DataE2' UNION ALL

SELECT 'EEE', 'DataE3'

--This is Left join that will produce dataset with all location groups.

SELECT

LG.LocationGroup

,RD.SomeOtherData

FROM #LocationGroups AS LG

LEFT OUTER JOIN #ReportData AS RD

ON LG.LocationGroup = RD.LocationGroup

--Cleanup

DROP TABLE #LocationGroups;

DROP TABLE #ReportData;