query-covering-indexes

Covering indexes include all columns needed by a query, enabling index-only scans that skip the table entirely.

Skills
Databases
0

What it does and how to use it

A skill that teaches Claude Code to do databases tasks well. It is packaged knowledge the model uses whenever it is relevant.

Install the skill (command above).
In Claude Code, describe what you need - the skill turns on by itself when the context fits.
No commands to memorize: you talk in plain language and the skill does the rest.

Install (Claude Code)

mkdir -p .claude/skills/query-covering-indexes && curl -fsSL https://doutorai.pt/data/lib/skills__query-covering-indexes.md -o .claude/skills/query-covering-indexes/SKILL.md

Paste this command into the terminal, in your project folder, and the component installs automatically.

Content

---
title: Use Covering Indexes to Avoid Table Lookups
impact: MEDIUM-HIGH
impactDescription: 2-5x faster queries by eliminating heap fetches
tags: indexes, covering-index, include, index-only-scan
---

## Use Covering Indexes to Avoid Table Lookups

Covering indexes include all columns needed by a query, enabling index-only scans that skip the table entirely.

**Incorrect (index scan + heap fetch):**

```sql
create index users_email_idx on users (email);

-- Must fetch name and created_at from table heap
select email, name, created_at from users where email = 'user@example.com';
```

**Correc

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