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

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?

Thanks for clarifying your problem,
Steve