Postgres 10

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create table customer as 
select * FROM ( VALUES ('e''QmfgLu/]sf]/sd' :: text), 
('foo''''bar'),  ('''foo''''bar'),
 ('foo''''bar''')) as s(name);

SELECT 4

select * from customer;

name

e'QmfgLu/]sf]/sd

foo''bar

'foo''bar

foo''bar'

SELECT 4

update customer set name=REGEXP_REPLACE(name, $$([^']|^)'(?!')$$, $$\1''$$ ,'g');

UPDATE 4

select * from customer;

name

e''QmfgLu/]sf]/sd

foo''bar

''foo''bar

foo''bar''

SELECT 4