Thread: 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?

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?