Last active
January 18, 2025 13:00
-
-
Save kidd/97cfcd7fb42fc2b03c8c812559bb01d2 to your computer and use it in GitHub Desktop.
arg_max example in duckdb
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| D create table test as SELECT i as i ,random() as r, i%4 as gr from generate_series(1,100) t(i); | |
| D select * from test; | |
| ┌───────┬──────────────────────┬───────┐ | |
| │ i │ r │ gr │ | |
| │ int64 │ double │ int64 │ | |
| ├───────┼──────────────────────┼───────┤ | |
| │ 1 │ 0.14984029697949075 │ 1 │ | |
| │ 2 │ 0.20274345139105418 │ 2 │ | |
| │ 3 │ 0.07478489612107744 │ 3 │ | |
| │ 4 │ 0.782259951294926 │ 0 │ | |
| │ 5 │ 0.2284793616804479 │ 1 │ | |
| │ 6 │ 0.041695246948323966 │ 2 │ | |
| │ 7 │ 0.7573347926971816 │ 3 │ | |
| │ 8 │ 0.73962961294214 │ 0 │ | |
| │ 9 │ 0.7779207988125088 │ 1 │ | |
| │ 10 │ 0.9389072358466003 │ 2 │ | |
| │ · │ · │ · │ | |
| │ · │ · │ · │ | |
| │ · │ · │ · │ | |
| │ 91 │ 0.6364273847165581 │ 3 │ | |
| │ 92 │ 0.18678856715252357 │ 0 │ | |
| │ 93 │ 0.6967327018959291 │ 1 │ | |
| │ 94 │ 0.9226525455998845 │ 2 │ | |
| │ 95 │ 0.8744859222496129 │ 3 │ | |
| │ 96 │ 0.868602423665254 │ 0 │ | |
| │ 97 │ 0.2760435713632134 │ 1 │ | |
| │ 98 │ 0.03305368778134084 │ 2 │ | |
| │ 99 │ 0.6663320953180856 │ 3 │ | |
| │ 100 │ 0.36892018499060536 │ 0 │ | |
| ├───────┴──────────────────────┴───────┤ | |
| │ 100 rows (20 shown) 3 columns │ | |
| └──────────────────────────────────────┘ | |
| D SELECT gr,max(r) from test group by all; -- did you notice this group by all? super cool! | |
| ┌───────┬────────────────────┐ | |
| │ gr │ max(r) │ | |
| │ int64 │ double │ | |
| ├───────┼────────────────────┤ | |
| │ 0 │ 0.9624206805514219 │ | |
| │ 1 │ 0.9922432776056797 │ | |
| │ 2 │ 0.9643812561324754 │ | |
| │ 3 │ 0.9202900638152589 │ | |
| └───────┴────────────────────┘ | |
| -- How could we get the id of the one that has the max r? | |
| -- https://stackoverflow.com/questions/3800551/select-first-row-in-each-group-by-group/7630564#7630564. | |
| -- not easy. But in some cases, arg_max can just do the job | |
| D SELECT gr,max(r),arg_max(i,r) from test group by gr; | |
| ┌───────┬────────────────────┬───────────────┐ | |
| │ gr │ max(r) │ arg_max(i, r) │ | |
| │ int64 │ double │ int64 │ | |
| ├───────┼────────────────────┼───────────────┤ | |
| │ 0 │ 0.9624206805514219 │ 60 │ | |
| │ 1 │ 0.9922432776056797 │ 61 │ | |
| │ 2 │ 0.9643812561324754 │ 22 │ | |
| │ 3 │ 0.9202900638152589 │ 23 │ | |
| └───────┴────────────────────┴───────────────┘ |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
@ANelson82 the advantage here is that you can sort the partitions only, not the entire list.
QUALIFYforces you sort the entire list,arg_maxdoes not.