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From: Frank Uray on 28 Apr 2010 09:20
Hi

Maybe you have to use count(somthing) to find out
if there are any rows.

CASE WHEN count(*) = 0
THEN no row
ELSE rows
END

Regards
Frank Uray

"trubar a" wrote:

> hi
>
> a) If a query/subquery doesn't find any matching rows, then it either
> returns NULL or no value at all, thus not even a NULL value. Based on
> what criteria does a query or a subquery return a NULL and when
> doesn't it return any results, not even a NULL value?
>
> b) I assume a scalar subquery will always return NULL, when no
> matching rows are found? I assume most-outer scalar query also returns
> NULL if no rows are found?
>
>
> c)
>
> SELECT FirstName, LastName, YEAR(BirthDate)
> FROM Persons
> WHERE YEAR(BirthDate) IN (SELECT YearReleased FROM Albums);
>
> * If subquery finds no results, is then a WHERE clause of an outer
> query translated into “WHERE YEAR(BirthDate) IN (null);”
>
> * If instead WHERE clause is translated into “WHERE YEAR(BirthDate) IN
> ();” then shouldn't that be an error condition, since how can
> YEAR(BirthDate) value be compared to nothing?
>
> thanx
> .
>
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