Re: In a view, how do I cause fields with possible NULLs to be treated as a blank string in a replace operation?

On 27 June 2011 17:53, Asfand Qazi (Sanger Institute)
<aq2(dot)sanger(at)gmail(dot)com> wrote:
> Hello,
>
> So I have am playing with a view to test the feasibility of a
> technique for storing some data.
>
> It basically goes something like this:
>
> CREATE VIEW formatted_table AS
>       SELECT name,
>              replace(some_template, '@', some_type) AS some_field
>         FROM some_table;
>
> some_template is something like 'foo(at)bar' or 'foobar' (note the
> missing template character).
>
> some_type is a single letter like 'a' or 'b', or it can be NULL.
>
> The above view works fine for rows where some_type is a letter, and
> some_field ends up as 'fooabar' or whatever.
>
> However, when some_type is NULL, some_field ends up as NULL as well.
> I understand that this is expected behaviour, but how do I cause the
> view to treat a some_type of NULL as an empty string, so that
> some_field simply ends up as 'foobar'?
>
> Hope that was clear.

Try coalesce: http://www.postgresql.org/docs/9.0/static/functions-conditional.html#AEN15541

So if foo is a null value, and you used COALESCE(foo, 'bar'), the
output would be 'bar', otherwise it would be whatever the value of foo
is.

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