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

From: Shaozhong SHI <[email-masked]>
Date: Thu, 9 Jun 2022 14:37:27 +0100

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?

Regards,

David

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From: Shaozhong SHI <[email-masked]>
Date: Thu, 9 Jun 2022 14:37:54 +0100

nodeid     link_type      primary
11           outflowlink       1
11              inflowlink      1
11              outflowlink     2

Regards,

David

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From: Steve Midgley <[email-masked]>
Date: Thu, 9 Jun 2022 12:16:12 -0700

> 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

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From: Shaozhong SHI <[email-masked]>
Date: Fri, 10 Jun 2022 00:13:20 +0100

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

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From: Steve Midgley <[email-masked]>
Date: Thu, 9 Jun 2022 16:25:27 -0700

On Thu, Jun 9, 2022 at 4:13 PM Shaozhong SHI <[email-masked]> wrote:

>>> 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.
>>>
>> 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