data-upsert

Using separate SELECT-then-INSERT/UPDATE creates race conditions. Use INSERT ... ON CONFLICT for atomic upserts.

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/data-upsert && curl -fsSL https://doutorai.pt/data/lib/skills__data-upsert.md -o .claude/skills/data-upsert/SKILL.md

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

Content

---
title: Use UPSERT for Insert-or-Update Operations
impact: MEDIUM
impactDescription: Atomic operation, eliminates race conditions
tags: upsert, on-conflict, insert, update
---

## Use UPSERT for Insert-or-Update Operations

Using separate SELECT-then-INSERT/UPDATE creates race conditions. Use INSERT ... ON CONFLICT for atomic upserts.

**Incorrect (check-then-insert race condition):**

```sql
-- Race condition: two requests check simultaneously
select * from settings where user_id = 123 and key = 'theme';
-- Both find nothing

-- Both try to insert
insert into settings (user_id, key, value)

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