Re: A function to find errors in groups in a table

On Thu, Jun 9, 2022 at 4:13 PM Shaozhong SHI <shishaozhong(at)gmail(dot)com> wrote:

> The first two can be regarded right. Certainly, the last one must be
> wrong. How can a primary flow get into a secondary flow?
>
> That is odd.
>
> Regards,
>
> David
>
> On Thursday, 9 June 2022, Steve Midgley <science(at)misuse(dot)org> wrote:
>
>>
>>
>> On Thu, Jun 9, 2022 at 6:37 AM Shaozhong SHI <shishaozhong(at)gmail(dot)com>
>> wrote:
>>
>>> There is a table full of grouped values like the following
>>>
>>> nodeid link_type primary
>>> 11 outflowlink 1
>>> 11 inflowlink 1
>>> 11 outflowlink 2
>>>
>>> Primary of 1 indicates a primary water course. Primary of 2 indicates a
>>> secondary water course.
>>>
>>> Obviously, one of the out flow links is an error, as its primacy value
>>> is 2. It is wrong that water flows from a primary water course into a
>>> secondary water course.
>>>
>>> How can a function can be designed to find and report such errors?
>>>
>>
>> Is the problem that there exists this row:
>>
>> 11 outflowlink 2
>>
>> But there is no corresponding row:
>>
>> 11 inflowlink 2
>>
>> So that you need to find all "orphan" rows that don't have a
>> corresponding member with the opposing data field inflowlink or
>> outflowlink where the "primary" column is the join field between the two
>> rows?
>>
>
You didn't answer my question, at least in a way I can understand, which
makes it hard to give you useful input on a solution.. Also, please try to
bottom post. This list asks posters to reply at the bottom of each email.

Steve