Neil Harkins <nharkins(at)well(dot)com> writes:
> Is this standard SQL behavior?
Yes. SQL92 6.13 <string value expression>, general rule 2:
2) If <concatenation> is specified, then let S1 and S2 be the re-
sult of the <character value expression> and <character factor>,
respectively.
a) If either S1 or S2 is the null value, then the result of the
<concatenation> is the null value.
...
regards, tom lane