Reach for this when you're staring at a slow query or need to write something gnarly with window functions and CTEs. It walks you through schema analysis, query optimization with EXPLAIN plans, and covering index design across PostgreSQL, MySQL, SQL Server, and Oracle. The workflow enforces a sub-100ms target and won't let you move on until you've eliminated sequential scans on large tables. What I like is the before/after examples showing correlated subquery rewrites and the quick reference for interpreting EXPLAIN ANALYZE output. It's opinionated about set-based operations and will push you toward EXISTS over COUNT, filtering before joins, and avoiding cursors when a single query will do.
npx skills add https://github.com/jeffallan/claude-skills --skill sql-pro