Which is the toughest query you have written until now?

Data Science, AI and ML
#1

SQL Question

#2

Nothing is tough if one decides to practice it. so continuous practice will make any tough query an easy one.

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#3

I wrote a reporting query once that was 700 lines long and visited 27 different tables in lookups or joins. It didn’t do any fancy stuff - just straight whereclause predicates and joining - but it was pretty gnarly and took 3 days to compose, debug, and tune.

It had to run in under 15 minutes on a DB world where the tables it visited had up to 5 billion records each, so it had to be well-tuned - even though it couldn’t help but be icky.

I was very, very careful with the formatting - and the query had about 1000 lines of comments around it so I could remember just what the heck I was doing when - as always happens with reports - the execs wanted stuff to be slightly different six months later

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