4 ms·

Thanks for the feedback! The first section is intentionally about self-joins since they get asked about in interviews, but other people have brought up that win

Thanks for the feedback! The first section is intentionally about self-joins since they get asked about in interviews, but other people have brought up that window functions are more efficient, so I'll add in those solutions as well. Sorry you feel that way! Thankfully my employer felt differently :)

beckingz 6y ago
If it runs fast fast enough or the business can wait long enough, slow and ugly is acceptable.
- thomzi12 6y ago
  Yes, in particular for data analysts using SQL to answer product/business questions in a one-off fashion
- MaxBarraclough 6y ago
  Unless the dataset grows, poorly optimised queries slow down superlinearly, and things start falling over.
- deepsun 6y ago
  That's exactly what I look against on interviews. Slow SQL queries tend to work fine for some time, and as data grows, they start failing. I'd want to hire a professional, who knows the perfect way of doing that, so for them it would be as easy to make it right, as to make it ugly.