SQL Server 2019

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CREATE TABLE #CustomerTable1 (CustomerID VARCHAR(25), CustomerName VARCHAR(25)) ;
INSERT INTO #CustomerTable1 VALUES ('0156', 'Frank'), ('0178', 'Darrull'), ('0908', 'Mary'), ('0785', 'Bertha');
CREATE TABLE #CustomerTable2 (CustomerIDFromTable1 varchar(25), LineNBR VARCHAR(25), ArbitraryID VARCHAR(25));
INSERT INTO #CustomerTable2 VALUES('0156', '1', '167483'), ('0156', '2', NULL), ('0156', '3', NULL), ('0156', '4', NULL),
                                    ('0178', '1', NULL), ('0178', '2', '873923'), ('0178', '3', NULL), ('0178', '4', NULL),
                                    ('0908', '1', NULL), ('0908', '2', NULL), ('0908', '2', NULL), ('0908', '4', NULL),
                                    ('0785', '1', NULL), ('0785', '2', NULL), ('0785', '3', NULL), ('0785', '4', NULL);
                                    CREATE TABLE #CustomerTable3 (ArbitraryIDFromTable2 VARCHAR(25), OtherID VARCHAR(25));
INSERT INTO #CustomerTable3 VALUES('167483', '89987648'), ('873923', '45564783');



22 rows affected

SELECT DISTINCT
    a.CustomerID AS CustomerIDFinal
    ,a.CustomerName
    ,c.OtherID
FROM #CustomerTable1 a
LEFT OUTER JOIN #CustomerTable2 b
    ON a.CustomerID = b.CustomerIDFromTable1
LEFT OUTER JOIN #CustomerTable3 c
    ON c.ArbitraryIDFromTable2 = b.ArbitraryID


CustomerIDFinal
CustomerName
OtherID


0156
Frank
null

0156
Frank
89987648

0178
Darrull
null

0178
Darrull
45564783

0785
Bertha
null

0908
Mary
null


SELECT
    a.CustomerID AS CustomerIDFinal
    ,a.CustomerName
    ,d.OtherID
FROM #CustomerTable1 a
LEFT OUTER JOIN 
(SELECT c.OtherId, b.CustomerIDFromTable1 FROM #CustomerTable3 c INNER JOIN
    #CustomerTable2 b ON c.ArbitraryIDFromTable2 = b.ArbitraryID
 ) d
    ON a.CustomerID = d.CustomerIDFromTable1


CustomerIDFinal
CustomerName
OtherID


0156
Frank
89987648

0178
Darrull
45564783

0908
Mary
null

0785
Bertha
null


SELECT
    a.CustomerID AS CustomerIDFinal
    ,a.CustomerName
    ,(SELECT c.OtherId FROM #CustomerTable3 c INNER JOIN
    #CustomerTable2 b ON c.ArbitraryIDFromTable2 = b.ArbitraryID WHERE a.CustomerID = b.CustomerIDFromTable1) OtherId
FROM #CustomerTable1 a


CustomerIDFinal
CustomerName
OtherId


0156
Frank
89987648

0178
Darrull
45564783

0908
Mary
null

0785
Bertha
null
CustomerIDFinal	CustomerName	OtherID
0156	Frank	null
0156	Frank	89987648
0178	Darrull	null
0178	Darrull	45564783
0785	Bertha	null
0908	Mary	null