Re: CONCAT returns null

Sterpu Victor <victor(at)caido(dot)ro> wrote:

> Hello
>
> I have this concat:
> CONCAT(f.nrfo, '/', TO_CHAR(fd1.validfrom, 'YYYY-MM-DD'), f2.nrfo, TO_CHAR
> (fd7.validfrom, 'YYYY-MM-DD'), DATE(fd5.validto)-DATE(fd1.validfrom))
> that works fine but when I change to this(I added a ' with '):
> ARRAY_AGG(CONCAT(f.nrfo, '/', TO_CHAR(fd1.validfrom, 'YYYY-MM-DD'), ' with ',
> f2.nrfo, TO_CHAR(fd7.validfrom, 'YYYY-MM-DD'), DATE(fd5.validto)-DATE
> (fd1.validfrom))) AS temp,
> then concat returns NULL.
> Why? I tried to add ' with '::VARCHAR and ' with '::TEXT but the result is
> still NULL.
>
> Thank you

NULL concat with a value returns NULL. You can avoid that using
COALESCE(value, ''), that returns the value, or, if the value NULL, ''.

Andreas
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