xlat expansion of absent VPs

Brian Candler b.candler at pobox.com
Tue Jun 18 08:27:51 CEST 2013

On 17/06/2013 16:44, Arran Cudbard-Bell wrote:
>>>   The idea is that a place-holder is better than silently expanding to
>>> an empty string.  An empty string means that data which is supposed to
>>> be 4 columns (for example) is now suddenly 3.  That's bad.
> No, because all values should be quoted (even integers and timestamps)
> and a "" or a '' is perfectly acceptable in the SQL world.
Aside: I think Postgres will reject a quoted string being used in an 
integer context.
> If users have an issue with it they can do %{%{FOO}:-_}, inserting
> _ by default is magical, inconsistent and unexpected.
> Besides, for SQL the proper behaviour would be %{%{FOO}:-NULL}, NULL
> being a value which is not known, anything else is arguably wrong.
Yes, that is the correct way to insert an integer attribute which may or 
may not be present.

This is easy for integers but not easy for strings, where in theory you 
want a quoted value if it's present but an unquoted NULL if it is not.

In practice, having to deal with NULL and empty string as distinct 
values is usually a pain, so I always write the empty string for missing 
attributes. And Oracle forces empty string to NULL in a varchar column.



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