The skills are vendor-neutral. They teach the standard spelling of each feature, name the correctness traps that LLMs reliably fall into, and map portability per feature across PostgreSQL, ...

What This Covers Set Operations – UNION (deduplicated), UNION ALL (all rows, faster), INTERSECT, and EXCEPT, comparing customer records across two yearly snapshots (2023 vs 2024). Joins – INNER JOIN, ...