SQL Server 2019

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE t
    (columnname varchar(1), value int, tbl varchar(1))
;
    
INSERT INTO t
    (columnname, value, tbl)
VALUES
    ('a', 1, 'X'),
    ('b', 2, 'X'),
    ('a', 3, 'X'),
    ('b', 4, 'X'),
    ('a', 5, 'X'),
    ('b', 6, 'X')
;
6 rows affected

select *
from t


columnname
value
tbl


a
1
X

b
2
X

a
3
X

b
4
X

a
5
X

b
6
X


select tbl
      ,a
      ,b
from
(
select *, (row_number() over(order by value)-1)/2 as rn
from   t
) t 
pivot(max(value) for columnname in(a, b)) p 


tbl
a
b


X
1
2

X
3
4

X
5
6