Re: syntax sugar for conditional check

On Fri, Apr 1, 2016 at 3:22 PM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:

> On 4/1/16 1:08 PM, Tom Lane wrote:
>
>> Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> writes:
>>
>>> Rather than this, I think an exclusive-or operator would be a lot more
>>> useful. The only difficulty I run into with CHECK constaints is when I
>>> want to ensure that only ONE condition is true.
>>>
>>
>> "bool != bool" works as XOR. If you need "exactly one of N" you could
>> do something like "(cond1::int + cond2::int + ...) = 1". We could
>> wrap some syntactic sugar around either of these, but it's not clear
>> to me that it'd be any more useful than a custom SQL function.
>>
>
> It would prevent having to re-create that function every time... :)

​And it would nicely complement our recent addition of "
num_nonnulls
​(variadic "any")​"

David J.