5 kyu
SQL Basics: Simple Hierarchical structure
2,884matt c
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SQL
Fundamentals
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Very nice exercise to understand recursion properly!
This is legit the best thing I have done with SQL. I didn't even know SQL had a recursive query.
Great kata for understanding recursive query!
In general the rules of defining levels: let employee of id = n have level m. Then we look for the employee whose manager's id is n and assign him level (m + 1). I don't think that's any kind of spoiler. Hope it clarifies the kata which is really cool.
very interesting kata, thank you
This one was lovely. I sometimes work with hierarchical data and have been struggling with 'levels' in postgres. This kata allowed me to pinpoint exactly what I was missing!
Great kata, surpisingly 'brain teasing'. This article really helped me conceptualise the problem in a better way: http://lextoumbourou.github.io/blog/posts/understanding-recursive-queries-in-postgresql/
Found it helpful, too, but original link is dead. Here's the achive link: https://web.archive.org/web/20200601114227/http://lextoumbourou.github.io/blog/posts/understanding-recursive-queries-in-postgresql/
This kata should more clearly specify how "level" should be defined.
Hope that helps.
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Very nice kata, tried it first months ago but could not understand what the level was supposed to be, came back to it today and managed to figure it out eventually.
Learned a lot, thanks :)
Thanks :)
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These articles helped me to resolve this kata:
https://www.citusdata.com/blog/2018/05/15/fun-with-sql-recursive-ctes/
http://blog.timothyandrew.net/blog/2013/06/24/recursive-postgres-queries/
Good articles, thank you, one of them pointed me in the right direction. This one helped me along them as well: https://www.essentialsql.com/recursive-ctes-explained/ After dealing mostly with ORMs and programmatic solutions of complex DB queries, this kata seemed confusing, but once solved, it's quite fascinating.
My solution appears to be generating the correct answers when I compare the actual vs expected tables, but the very last test gives this error:
should should return the expected results ✘ expected true to respond to
true?or perhaps you meantbe trueorbe_truthy?
this is a codewards error.
Great Kata. I wanted to make something similar (as a basic version of my Hierarchy Kata), but now you have been faster :) Looks like most of SQL's basic concepts have already been covered.
By the way, you have an typo in your description: You are describing the "employeees" table, but it's actual name is "employees". Count the 'e's ;)
thanks, fixed