# Dolt — The SQL Database You Can Fork, Clone, Branch and Merge

> The world's first version-controlled SQL database. Dolt combines MySQL compatibility with Git-style branching, diffing and merging so schemas and data can be reviewed and pull-requested.

## Install

Save in your project root:

# Dolt — The SQL Database You Can Fork, Clone, Branch and Merge

## Quick Use
```bash
# Install
curl -L https://github.com/dolthub/dolt/releases/latest/download/install.sh | sudo bash

# Init, branch, commit
mkdir shop && cd shop
dolt init
dolt sql -q "CREATE TABLE items (id INT PRIMARY KEY, name VARCHAR(64), price DECIMAL(10,2));"
dolt sql -q "INSERT INTO items VALUES (1,'Mug',9.99);"
dolt add . && dolt commit -m "seed catalogue"

dolt checkout -b promo
dolt sql -q "UPDATE items SET price = price * 0.8;"
dolt diff main promo          # row-level diff
dolt merge promo               # Git-style merge back into main
```

## Introduction
Dolt is an open-source SQL database that stores its tables, schemas and commit history in a Merkle DAG, so every operation you expect from Git — clone, branch, diff, merge, log, blame, push, pull — works on live data. It speaks the MySQL wire protocol, so existing drivers, ORMs and BI tools connect unchanged.

## What Dolt Does
- Serves SQL over the MySQL protocol with a large subset of MySQL 8 syntax.
- Versions both schema and rows: every `dolt commit` is content-addressed.
- Produces row-level diffs between branches or commits with `dolt diff` or `dolt_diff_<table>`.
- Merges branches, detecting schema and data conflicts that you can resolve in SQL.
- Pushes and pulls repositories to DoltHub or any S3-compatible remote.

## Architecture Overview
Under the hood Dolt stores data in Prolly Trees — B-tree-like structures with content-addressed chunks that make cheap structural sharing possible across branches. A commit references a root hash covering every table, so diffing two commits is an O(changes) tree walk. The SQL layer is a query engine that reads and writes Prolly Trees transactionally and speaks the MySQL protocol.

## Self-Hosting & Configuration
- Install the single Go binary; no external dependencies.
- Run `dolt sql-server` to expose the MySQL protocol on port 3306 for BI tools and drivers.
- Configure users and grants with standard `CREATE USER` / `GRANT` statements.
- Back up by cloning the repo to S3/GCS using `dolt remote add` + `dolt push`.
- Use `doltgres` when you need the PostgreSQL wire protocol instead.

## Key Features
- Time-travel queries: `SELECT * FROM items AS OF 'HEAD~3';`.
- Dolt functions: `dolt_commit()`, `dolt_merge()`, `dolt_branch()` callable from SQL.
- `dolt_history_<table>` and `dolt_diff_<table>` system tables for auditing.
- CI integration via `dolt ci` to test data changes the way you test code.
- Free public hosting for open datasets on DoltHub.

## Comparison with Similar Tools
- **Git LFS / DVC** — version files, not live SQL tables.
- **TerminusDB** — graph-oriented, not MySQL-compatible.
- **LakeFS** — Git semantics on object storage, but no SQL engine.
- **Liquibase / Flyway** — version schema migrations only, not data.
- **Postgres + temporal tables** — auditing but no branching or merging.

## FAQ
**Q:** Is Dolt a drop-in replacement for MySQL?
A: For most CRUD workloads, yes. Some replication and niche engine features are not implemented.
**Q:** How big can a Dolt database get?
A: Multi-hundred-GB repos are in production; performance scales with Prolly Tree chunking.
**Q:** Can I branch terabytes without copying?
A: Yes — branches share chunks, so they are metadata operations.
**Q:** Is Dolt good for OLAP?
A: It is tuned for OLTP-ish data with versioning. For heavy analytics, export to DuckDB or ClickHouse.

## Sources
- https://github.com/dolthub/dolt
- https://docs.dolthub.com/

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Source: https://tokrepo.com/en/workflows/f8c7831d-391f-11f1-9bc6-00163e2b0d79
Author: AI Open Source