[feat] New skill: language-sql

[lugassawan]

Goal

A language-sql skill encodes SQL query and schema engineering idioms so agents give principled guidance when working with relational databases.

Motivation

SQL is orthogonal to all other language skills — it appears inside Python, Go, TypeScript, and Java codebases alike. No language skill currently covers SQL. Agents default to training-data patterns when evaluating query efficiency, transaction isolation, or window function usage.

Surface

• Skill — language-*

Sketch (optional)

File: skills/language-sql/SKILL.md

Key topics:

• Query optimization fundamentals (index usage, avoid SELECT *, predicate pushdown)
• EXPLAIN/EXPLAIN ANALYZE reading
• Schema design: normalization, foreign keys, constraint placement
• Transaction isolation levels and their practical implications
• Deadlock avoidance patterns
• Window functions: ROW_NUMBER, RANK, LAG, LEAD — when and how
• CTEs vs subqueries: readability and performance tradeoffs
• Pagination patterns (keyset vs offset)

Acceptance (optional)

• skills/language-sql/SKILL.md exists with valid frontmatter
• scripts/validate.py passes

[ejscott1]

I’m interested in working on this.

One thing I noticed: the issue sketch says skills/languages/language-sql/skill.md, but the contributing guide says skills must use the flat layout skills/<skill-name>/SKILL.md.

I’ll follow the existing language skill pattern and add skills/language-sql/SKILL.md, then update agents/shared/skills.md and any catalog references needed so scripts/validate.sh passes.

Does that sound right?

[lugassawan]

Yes, that's correct. Will revise it.