PostgreSQL update Primary key column with random integer values

Question

I have a table with the Integet column as a Primary key. For testing purpose, I want to restore the table to a test server and randomly change the ID column.

Something like

select ('9985'||id)::int from table;

But updating is not working as I expected.

update test set id=(select ('9985'||id)::int from test);

ERROR:

ERROR:  more than one row returned by a subquery used as an expression

Answer 1

What about:

 update test set id = ('9985'||id)::int

You don't need the from part