SQL Optimization Patterns
ynulihao/AgentSkillOS
Master SQL query optimization, indexing strategies, and EXPLAIN analysis to dramatically improve database performance and eliminate slow queries.
Staff+ DBA SQL patterns targeting what Claude's defaults miss - multi-column statistics, operator classes, keyset pagination, silent performance anti-patterns.
Install Writing SQL
$ npx skills add rileyhilliard/claude-essentials --skill writing-sql -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install rileyhilliard/claude-essentials writing-sql --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/rileyhilliard/claude-essentials.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/ce/skills/writing-sql .claude/skills/writing-sql && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "writing-sql" agent skill from https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sql into .claude/skills/writing-sql/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "writing-sql", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sqlType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add rileyhilliard/claude-essentials --skill writing-sql -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install rileyhilliard/claude-essentials writing-sql --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rileyhilliard/claude-essentials.git skills-src && mkdir -p .agents/skills && cp -r skills-src/plugins/ce/skills/writing-sql .agents/skills/writing-sql && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "writing-sql" agent skill from https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sql into .agents/skills/writing-sql/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "writing-sql", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add rileyhilliard/claude-essentials --skill writing-sql -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install rileyhilliard/claude-essentials writing-sql --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rileyhilliard/claude-essentials.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/plugins/ce/skills/writing-sql .cursor/skills/writing-sql && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "writing-sql" agent skill from https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sql into .cursor/skills/writing-sql/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "writing-sql", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/rileyhilliard/claude-essentials.git --path plugins/ce/skills/writing-sql--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add rileyhilliard/claude-essentials --skill writing-sql -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install rileyhilliard/claude-essentials writing-sql --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rileyhilliard/claude-essentials.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/plugins/ce/skills/writing-sql .gemini/skills/writing-sql && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "writing-sql" agent skill from https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sql into .gemini/skills/writing-sql/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "writing-sql", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install rileyhilliard/claude-essentials writing-sqlInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add rileyhilliard/claude-essentials --skill writing-sql -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/rileyhilliard/claude-essentials.git skills-src && mkdir -p .github/skills && cp -r skills-src/plugins/ce/skills/writing-sql .github/skills/writing-sql && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "writing-sql" agent skill from https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sql into .github/skills/writing-sql/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "writing-sql", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add rileyhilliard/claude-essentials --skill writing-sql -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install rileyhilliard/claude-essentials writing-sql --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rileyhilliard/claude-essentials.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/plugins/ce/skills/writing-sql .opencode/skills/writing-sql && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "writing-sql" agent skill from https://github.com/rileyhilliard/claude-essentials/tree/main/plugins/ce/skills/writing-sql into .opencode/skills/writing-sql/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "writing-sql", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
writing-sql- GitHub stars
- 130
- Token cost
- ~627 tokens
- SKILL.md length
- 211 words
- Files
- 5 (incl. references)
- Skills in repo
- 17
- Repo updated
- First seen
- Licence
- MIT
At a glance
Staff+ DBA SQL patterns targeting what Claude's defaults miss - multi-column statistics, operator classes, keyset pagination, silent performance anti-patterns.
- Writing complex SQL
- SKILL.md covers Topic Navigation and Iron Rules
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- Reviewing queries
What it does
Writing SQL is an agent skill from rileyhilliard/claude-essentials. Staff+ DBA SQL patterns targeting what Claude's defaults miss - multi-column statistics, operator classes, keyset pagination, silent performance anti-patterns. Use when writing complex SQL, reviewing queries, adding indexes, or optimizing slow queries.
Its SKILL.md is about 630 tokens, which your agent loads only when the skill is triggered. The skill folder holds 5 other files, including reference files (for example `references/aggregation-patterns.md`, `references/extended-statistics.md` and `references/index-internals.md`).
It sits in Databases, covering SQL, Statistics and Query optimization. It works with SQL. The licence is MIT.
When your agent uses it
- Writing complex SQL
- Reviewing queries
- Optimizing slow queries
Example prompts
- “/writing-sql”
What it can do on your machine
Read from SKILL.md and the folder at commit 3a67a01. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Writing SQL loads about 627 tokens when it runs, and up to ~6.8k if it reads all its reference files. Until then it costs about 66 tokens; SKILL.md has 211 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from rileyhilliard/claude-essentials at commit 3a67a01, republished under its MIT licence (© rileyhilliard). 211 words, ~627 tokens.
Download SKILL.mdSave it as
.claude/skills/writing-sql/SKILL.md (or your agent's skills folder). This skill also uses 4 other files; get the full folder from GitHub.- name
- writing-sql
- description
- Staff+ DBA SQL patterns targeting what Claude's defaults miss - multi-column statistics, operator classes, keyset pagination, silent performance anti-patterns. Use when writing complex SQL, reviewing queries, adding indexes, or optimizing slow queries.
Writing SQL
Core principle: Every query you write has an execution plan. Write SQL with that plan in mind, not just the result.
This skill covers only what Claude's defaults miss. Topics already handled by managing-databases/postgres-querying.md (LATERAL, CTE materialization, DISTINCT ON, EXPLAIN red flags, ROWS vs RANGE) are not repeated here.
Topic Navigation
| Task | Load |
|---|---|
| Planner picking bad plans on multi-column WHERE | extended-statistics.md |
| LIKE search not using index, text pattern matching | index-internals.md |
| Composite index column ordering, INCLUDE clause | index-internals.md |
| Type mismatch between param and column silently bypassing index | index-internals.md |
| Conditional aggregation, pivot queries, subtotals | aggregation-patterns.md |
| GROUPING SETS, ROLLUP, CUBE | aggregation-patterns.md |
| NULL edge cases in aggregates and window functions | aggregation-patterns.md |
| Paginating large result sets | query-anti-patterns.md |
| NOT IN returning zero rows unexpectedly | query-anti-patterns.md |
| DISTINCT added to fix duplicate rows | query-anti-patterns.md |
| Correlated subqueries in SELECT list | query-anti-patterns.md |
| Functions in WHERE bypassing indexes | query-anti-patterns.md |
Iron Rules
These apply to every query, no exceptions:
- Never paginate with OFFSET on large tables. Use keyset pagination.
- Never use NOT IN when the subquery column is nullable. Use NOT EXISTS.
- Always match parameter types to column types exactly. Implicit casts bypass indexes.
- Replace CASE WHEN inside aggregates with FILTER. It's cleaner and semantically correct.
- When a multi-column WHERE produces bad estimates, add extended statistics before adding hints or rewrites.
© rileyhilliard, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 4 other files (references) in plugins/ce/skills/writing-sql of rileyhilliard/claude-essentials.
- SKILL.md
- references/aggregation-patterns.md
- references/extended-statistics.md
- references/index-internals.md
- references/query-anti-patterns.md
Open the folder on GitHubat commit 3a67a01
Compare with similar skills
Writing SQL next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Writing SQL this skillrileyhilliard/claude-essentials | 130 | — | ~627 | Automated safety check: Pass | MIT | |
| SQL Optimization Patternsynulihao/AgentSkillOS | 617 | 10 repos | ~3.3k | Automated safety check: Pass | None | |
| Query Engine Designrevfactory/claude-code-harness | 120 | — | ~474 | Automated safety check: Pass | None | |
| SQL Optimization Patternssickn33/agentic-awesome-skills | 47k | 1 repos | ~566 | Automated safety check: Pass | MIT | |
| SQL Database Assistantborghei/Claude-Skills | 874 | — | ~1.5k | Automated safety check: Pass | MIT | |
| SQL Optimization InterviewerPrepLabsAI/InterviewMentor | 112 | — | ~2.1k | Automated safety check: Pass | MIT |
Similar skills
Query Engine Design
revfactory/claude-code-harness
SQL query engine design and implementation guide. An agent skill from revfactory/claude-code-harness.
SQL Optimization Patterns
sickn33/agentic-awesome-skills
Diagnose slow SQL with query plans, preserve query results, and verify indexing or query changes against representative data.
SQL Database Assistant
borghei/Claude-Skills
This skill should be used when the user asks to "optimize SQL queries", "explore database schemas", "generate migration SQL", "analyze query performance", or "document database structure".
SQL Optimization Interviewer
PrepLabsAI/InterviewMentor
A Data Engineering interviewer focused on database performance.
Query Optimize
lazyFrogLOL/Harness_Engineering
Guidance for SQL query optimization tasks. An agent skill from lazyFrogLOL/Harness_Engineering.
More from rileyhilliard/claude-essentials
All 17 skills in this repoHandling Errors
rileyhilliard/claude-essentials
Prevents silent failures and context loss in error handling.
Planning Products
rileyhilliard/claude-essentials
Defines product features from a PM perspective (JTBD, competitive research, scope negotiation) before technical planning.
Writing Tests
rileyhilliard/claude-essentials
Writes behavior-focused tests using Testing Trophy model with real dependencies.
Optimizing Performance
rileyhilliard/claude-essentials
Measure-first performance optimization that balances gains against complexity.
Architecting Systems
rileyhilliard/claude-essentials
Guides clean, scalable system architecture during the build phase.
Design
rileyhilliard/claude-essentials
Enforces precise, minimal design for dashboards and admin interfaces.
Related
Works with
Categories
Questions about Writing SQL
What does Writing SQL do?
Staff+ DBA SQL patterns targeting what Claude's defaults miss - multi-column statistics, operator classes, keyset pagination, silent performance anti-patterns. Writing SQL is an agent skill from rileyhilliard/claude-essentials. Staff+ DBA SQL patterns targeting what Claude's defaults miss - multi-column statistics, operator classes, keyset pagination, silent performance anti-patterns.
When should I use Writing SQL?
Writing SQL fits situations like: writing complex SQL; reviewing queries; optimizing slow queries.
How do I install Writing SQL in Claude Code?
Run `npx skills add rileyhilliard/claude-essentials --skill writing-sql -a claude-code`. Or copy the skill folder (plugins/ce/skills/writing-sql in rileyhilliard/claude-essentials) into .claude/skills/writing-sql in your project. Claude Code loads it when a task matches its description.
How do I install Writing SQL in Codex?
Run `npx skills add rileyhilliard/claude-essentials --skill writing-sql -a codex`. Or copy the skill folder (plugins/ce/skills/writing-sql in rileyhilliard/claude-essentials) into .agents/skills/writing-sql in your project. Codex loads it when a task matches its description.
Can I use Writing SQL in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add rileyhilliard/claude-essentials --skill writing-sql -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/writing-sql, .gemini/skills/writing-sql, .github/skills/writing-sql and .opencode/skills/writing-sql in your project.
What does Writing SQL need to run?
SKILL.md names no scripts, command-line tools or credentials: Writing SQL is instructions for the agent only.
Does Writing SQL access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Writing SQL safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Writing SQL use?
Writing SQL is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Writing SQL use?
About 627 tokens (SKILL.md is roughly 2.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 6.2k tokens, read only when the agent opens those files.
What are the alternatives to Writing SQL?
Skills that share tags, products or a category with Writing SQL: SQL Optimization Patterns (ynulihao/AgentSkillOS, 617 stars), Query Engine Design (revfactory/claude-code-harness, 120 stars), SQL Optimization Patterns (sickn33/agentic-awesome-skills, 47k stars) and SQL Database Assistant (borghei/Claude-Skills, 874 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Writing SQL?
rileyhilliard (a GitHub user) maintains it in rileyhilliard/claude-essentials, which has 130 GitHub stars. The repository holds 17 skills in this directory. The repository was last updated on August 18, 2026.
Source: rileyhilliard/claude-essentials on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.