declare @tab table (col1 char(2))
insert into @tab values
('A1'),
('A2'),
('A3'),
('B1'),
('B2'),
('B3')
SELECT
A.Col1,
B.Col1
FROM
(
SELECT
ROW_NUMBER() OVER(PARTITION BY LEFT(Col1,1) ORDER BY Col1) AS RowNum,
Col1
FROM
@tab
WHERE
LEFT(Col1,1) = 'A'
) AS A
FULL OUTER JOIN
(
SELECT
ROW_NUMBER() OVER(PARTITION BY LEFT(Col1,1) ORDER BY Col1) AS RowNum,
Col1
FROM
@tab
WHERE
LEFT(Col1,1) = 'B'
) AS B
ON
A.RowNum = B.RowNum