A function to find errors in groups in a table

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

On Thu, Jun 9, 2022 at 6:37 AM Shaozhong SHI <shishaozhong@gmail.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

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@misuse.org> wrote:

On Thu, Jun 9, 2022 at 4:13 PM Shaozhong SHI <shishaozhong@gmail.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@misuse.org> wrote:

On Thu, Jun 9, 2022 at 6:37 AM Shaozhong SHI <shishaozhong@gmail.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