How do I install the Query Rewriter skill?

Run npx skillmds@latest add huifer/query-rewriter in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Query Rewriter safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Query Rewriter?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Query Rewriter free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Query Rewriter?

huifer (@huifer) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Query Rewriter by huifer — Agent Skill

Name: Query Rewriter
Author: huifer

File contents

SQL Query Rewriting Expert

Common Anti-Patterns

Anti-Pattern	Problem	Reference
SELECT *	Fetches unnecessary data	`references/select-star.md`
N+1 queries	Too many round trips	`references/n-plus-one.md`
IN with subquery	May process too many rows	`references/exists-vs-in.md`
OR across columns	Prevents index usage	`references/or-optimization.md`
OR conditions	Cannot use index	`references/union-instead-of-or.md`
Type mismatch	Implicit conversion	`references/implicit-conversion.md`

Audit Workflow

Step 1: Identify Problem Patterns

Check for:

SELECT * usage
N+1 query patterns
IN with large subqueries
OR conditions across columns
Type mismatches

Step 2: Match Anti-Pattern

Identify which anti-pattern the query matches and apply the corresponding solution from the reference file.

Step 3: Apply Rewrite

Follow the specific reference file for detailed instructions.

Step 4: Verify Improvement

EXPLAIN ANALYZE <rewritten_query>;

Benchmark Reference

Optimization	Before	After	Improvement
SELECT * → specific	100ms	20ms	80%
N+1 → batch	500ms	50ms	90%
IN → EXISTS	500ms	50ms	90%
OR → UNION	200ms	20ms	90%
Type fix	150ms	2ms	98.7%

Output Format

## Query Rewriting Report

### 1. Original Query
```sql
<original_query>

2. Anti-Patterns Detected

Pattern	Problem	Reference
...	...	...

3. Recommended Rewrite

<optimized_query>

4. Expected Improvement

Query time: Xms → Yms (Z% faster)
Rows processed: X → Y (Z% reduction)

5. Implementation

Reference: references/.md

---name: query-rewriterdescription: SQL query rewriting expert. Identifies inefficient query patterns and provides optimized alternatives. Trigger when user mentions query optimization, SQL rewriting, or query performance.---# SQL Query Rewriting Expert## Common Anti-Patterns| Anti-Pattern | Problem | Reference ||--------------|---------|-----------|| SELECT * | Fetches unnecessary data | `references/select-star.md` || N+1 queries | Too many round trips | `references/n-plus-one.md` || IN with subquery | May process too many rows | `references/exists-vs-in.md` || OR across columns | Prevents index usage | `references/or-optimization.md` || OR conditions | Cannot use index | `references/union-instead-of-or.md` || Type mismatch | Implicit conversion | `references/implicit-conversion.md` |## Audit Workflow### Step 1: Identify Problem PatternsCheck for:- SELECT * usage- N+1 query patterns- IN with large subqueries- OR conditions across columns- Type mismatches### Step 2: Match Anti-PatternIdentify which anti-pattern the query matches and apply the corresponding solution from the reference file.### Step 3: Apply RewriteFollow the specific reference file for detailed instructions.### Step 4: Verify Improvement```sqlEXPLAIN ANALYZE <rewritten_query>;```## Benchmark Reference| Optimization | Before | After | Improvement ||--------------|--------|-------|-------------|| SELECT * → specific | 100ms | 20ms | 80% || N+1 → batch | 500ms | 50ms | 90% || IN → EXISTS | 500ms | 50ms | 90% || OR → UNION | 200ms | 20ms | 90% || Type fix | 150ms | 2ms | 98.7% |## Output Format```## Query Rewriting Report### 1. Original Query```sql<original_query>```### 2. Anti-Patterns Detected| Pattern | Problem | Reference ||---------|---------|-----------|| ... | ... | ... |### 3. Recommended Rewrite```sql<optimized_query>```### 4. Expected Improvement- Query time: Xms → Yms (Z% faster)- Rows processed: X → Y (Z% reduction)### 5. ImplementationReference: references/<case-name>.md```

Frequently asked questions

Query Rewriter