ITPUB

Mar 25, 2023 · Big Data

Mastering Efficient SQL in ODPS: Union, Count‑Distinct, and Join Optimizations

This article walks through common SQL development scenarios on ODPS, examining why naïve UNION and COUNT DISTINCT can be slow, how to rewrite queries with GROUP BY, UNION ALL, JSON aggregation, and map‑join techniques, and shows the resulting execution‑plan improvements with concrete code and performance numbers.