Re: migrating from mysql: need to convert empty string to null

"Dave Lee" <davelee.com@gmail.com> writes:
> and I notice that there isn't any rows specified for converting
> varchar or text to int. Which raises the question, if I run:

> SELECT '123'::int;

> What conversion is actually happening here?

None.  There is no type coercion there --- what that is really
specifying is invocation of the int data type's input function
on the given string.

I don't think your approach is going to work; you would have to
make your client programs emit things like

    insert into mytab(integercol) values (''::varchar)

in order to get a runtime varchar-to-int cast to be applied.
At that point you might as well fix them properly.

            regards, tom lane