update 1st column value to 2nd column

create table test
(
col1 int,
col2 int
)

insert into test values(1,4),(10,5),(2,10),(5,9)

select * from test

UPDATE test SET col1=col2, col2=col1

select * from test

select * from test

update t1
set t1.col1=t2.c1,t1.col2=t2.c2
from test t1
join
(
select col2 as c1,col1 as c2 from test
)t2
on t1.col1=t2.c2

select * from test

DECLARE @tmp TABLE (id1 INT, id2 INT)
INSERT INTO @tmp (id1, id2)
SELECT 1, 5
UNION ALL SELECT 2, 8
UNION ALL SELECT 3, 6

UPDATE t1
    SET t1.id1 = t2.id2,
        t1.id2 = t2.id1
FROM @tmp AS t1 INNER JOIN @tmp AS t2 ON t1.id1 = t2.id1

SELECT *
FROM @tmp

IF(SELECT OBJECT_ID('TEMPDB..#TEM')) IS NOT NULL
DROP TABLE #TEM
SELECT TOP 0 * INTO #TEM  FROM TABLENAME


INSERT INTO #TEM SELECT id2,ID1 FROM TABLENAME
SELECT * FROM #TEM

UPDATE tableName SET Column1=Column2, Column2=Column1