SQL Server 2017

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create table mytable (column1 varchar(10), column2 varchar(10))
insert into mytable (column1) values ('ABCHi');
1 rows affected

insert into mytable (column1) values ('TER12');
1 rows affected

insert into mytable (column1) values ('WhatE');
1 rows affected

with Dictionary as(
  select 'ABCHi' as column1, 'newOH' as column2 
  union all
  select 'TER12' as column1, 'Meow2' as column2 
  union all
  select 'WhatE' as column1, 'BMW26' as column2
  )
UPDATE t
SET  t.column2=dictionary.column2
FROM mytable t JOIN Dictionary ON t.column1 = Dictionary.column1
3 rows affected

select * from mytable


column1
column2


ABCHi
newOH

TER12
Meow2

WhatE
BMW26