I came up this:

create table testing (retained int, dropped int)

insert into testing (retained, dropped)

select 767884, 157441 union all

select 1046261, 157441 union all

select 1055257, 157441 union all

select 157441, 73635 union all

select 767884, 73635 union all

select 1046261, 73635 union all

select 1055257, 73635 union all

select 1046261, 767884 union all

select 1055257, 767884 union all

select 1055257, 1046261

select * from testing

ORDER BY dropped,retained;

WITH UpdateValues AS (

SELECT

MAX(retained) AS NewValue,

dropped

FROM

testing

GROUP BY

dropped

)

UPDATE t SET

retained = uv.NewValue

FROM

testing t

INNER JOIN UpdateValues uv

ON (t.dropped = uv.dropped);

select * from testing

ORDER BY dropped,retained;

DROP TABLE testing;