Challenges students face when learning to work with relational databases and SQL

Re:Challenges students face when learning to work with relat... by weaksauce on Sunday August 29, 2021 @06:37PM (#28351113)

I'm not sure if you are replying to the wrong person but the question has nothing to do with a total sum of ids...

the question was: "List all pairs of customer IDs who live on a street with the same name but in a different city." listed under self-join

that said i haven't wrangled with raw sql in a spell so the reading on window functions is interesting.

[ Parent | on HN ]

Re:Challenges students face when learning to work with relat... by fifilura on Monday August 30, 2021 @02:28AM (#28353239)

1. GP mentioned hairy self joins 2. You replied with an example 3. I pointed out that there are other examples.

That said, I have a feeling your duplicates can be fixed by adding the requirement that c.cid < c2.cid

Not sure a window function would help in this particular situation, but they are there to help in more mundane examples.

[ Parent | on HN ]

Re:Challenges students face when learning to work with relat... by weaksauce on Monday August 30, 2021 @02:11PM (#28358922)

I see how it can be read that way yeah. they mentioned the study used a self join problem that they couldn't likely figure out so I looked at the paper and quickly did it off the top of my head. the less than predicate does indeed do the trick.

[ Parent | on HN ]