CREATE TABLE #WO(WO int, RD varchar(10))

INSERT INTO #WO VALUES (122 ,'asas')
INSERT INTO #WO VALUES (123 ,'der')
INSERT INTO #WO VALUES (124 ,'wer3er')
INSERT INTO #WO VALUES (124 ,'rtre')
INSERT INTO #WO VALUES (124 ,'hehehe')
 
 SELECT *, CASE WHEN Row_no > 1 THEN
CONVERT(varchar, WO)+  CHAR(63 + Row_no)
ELSE CONVERT(varchar,WO) END FROM 
(Select * , 
Row_Number() OVER (Partition BY WO ORDER BY WO) as Row_No
FROM #WO) #t1

CREATE TABLE #WO(WO int, RD varchar(10))

INSERT INTO #WO VALUES (122 ,'asas')
INSERT INTO #WO VALUES (123 ,'der')
INSERT INTO #WO VALUES (124 ,'wer3er')
INSERT INTO #WO VALUES (124 ,'rtre')
 
 SELECT WO, CASE WHEN  RowCnt > 1 THEN
'(' +  CHAR(96 + Row_no) + ') ' + RD 
ELSE RD END FROM 
(Select * , 
Row_Number() OVER (Partition BY WO ORDER BY WO) as Row_No
FROM #WO) #t1 INNER JOIN (SELECT wo AS Wo1,COUNT(*) AS RowCnt FROM #wo GROUP BY WO) a ON #t1.WO = a.wo1

SELECT *, CASE WHEN Row_no > 1 THEN
CONVERT(varchar, WO)+  CHAR(63 + Row_no)
ELSE CONVERT(varchar,WO) END FROM 
(Select * , 
Row_Number() OVER (Partition BY WO ORDER BY WO) as Row_No
FROM #WO) #t1

SELECT WO, CASE WHEN  RowCnt > 1 THEN
CONVERT(varchar, WO) + '(' +  CHAR(96 + Row_no) + ') ' 
ELSE CONVERT(varchar, WO) END FROM 
(Select * , 
Row_Number() OVER (Partition BY WO ORDER BY WO) as Row_No
FROM #WO) #t1 
INNER JOIN (SELECT wo AS Wo1,COUNT(*) AS RowCnt FROM #wo GROUP BY WO) a 
ON #t1.WO = a.wo1

SELECT  CASE WHEN  RowCnt > 1 THEN
CONVERT(varchar, WO) + '(' +  CHAR(96 + Row_no) + ') ' 
ELSE CONVERT(varchar, WO) END, RD FROM 
(Select * , 
Row_Number() OVER (Partition BY WO ORDER BY WO) as Row_No
FROM #WO) #t1 
INNER JOIN (SELECT wo AS Wo1,COUNT(*) AS RowCnt FROM #wo GROUP BY WO) a 
ON #t1.WO = a.wo1