query-composite-indexes

When queries filter on multiple columns, a composite index is more efficient than separate single-column indexes.

Skills
Databases
4

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

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

Content

---
title: Create Composite Indexes for Multi-Column Queries
impact: HIGH
impactDescription: 5-10x faster multi-column queries
tags: indexes, composite-index, multi-column, query-optimization
---

## Create Composite Indexes for Multi-Column Queries

When queries filter on multiple columns, a composite index is more efficient than separate single-column indexes.

**Incorrect (separate indexes require bitmap scan):**

```sql
-- Two separate indexes
create index orders_status_idx on orders (status);
create index orders_created_idx on orders (created_at);

-- Query must combine both indexes (slow

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