Albe Laurenz <laurenz.albe@wien.gv.at> writes:
> You cannot specify a conversion function while altering
> a column's type, you'd have to use a new column like this:
Sure you can; that's the whole point of the USING option.
It'd look something like
ALTER TABLE test ALTER COLUMN val TYPE varchar(255) USING convert(val);
with whatever is appropriate in place of convert().
But the real question of course is what is "appropriate" for the OP's
situation --- he didn't specify exactly what he's got in his bytea
column or how that should be converted to varchar.
regards, tom lane
