Introduction

chain-builder is a typed, dialect-aware SQL query builder for Rust. One builder API, generic over a Dialect marker type, targets PostgreSQL, MySQL, and SQLite — mixing dialects is a compile error, not a runtime surprise.

Two safety properties hold everywhere in the API, by construction:

• Values are always bound parameters. Anything you pass as a value (where_eq("status", "active"), insert(...), limit(...)) becomes a placeholder ($1 on Postgres, ? on MySQL/SQLite) plus a typed bind — it is never interpolated into the SQL string.
• Identifiers are always escaped. Table, column, and database names are quoted with the dialect's quote character ("users" on Postgres/SQLite, `users` on MySQL), with embedded quote characters doubled.

The only places these guarantees do not apply are the explicitly named *_raw escape hatches — see the Security Model for the complete inventory.

A taste

let (sql, binds) = QueryBuilder::<Postgres>::table("users")
    .select(["id"])
    .where_eq("status", "active")
    .to_sql();
// SELECT "id" FROM "users" WHERE "status" = $1

Swap Postgres for MySql and the same chain renders backticks and ? placeholders. See Getting Started for installation and a full walkthrough.

Dialect feature matrix

Feature	PostgreSQL	MySQL	SQLite
Placeholder style	$N (numbered)	? (positional)	? (positional)
Identifier quote char	"	`	"
Upsert style	ON CONFLICT (...) DO NOTHING / DO UPDATE SET …	INSERT IGNORE / ON DUPLICATE KEY UPDATE …	ON CONFLICT (...) DO NOTHING / DO UPDATE SET …
RETURNING	✅ supported	❌ not supported (clause is a no-op)	✅ supported
DISTINCT ON	✅ supported	❌ build error	❌ build error
Row locking (FOR UPDATE / FOR SHARE)	✅ supported	✅ supported	❌ silent no-op (SQLite locks the whole database)
Native ILIKE	✅ native operator	lowered to LOWER(col) LIKE LOWER(?)	lowered to LOWER(col) LIKE LOWER(?)

The Dialect Differences page expands each row with prose notes and examples.

Where to find things

• crates.io — https://crates.io/crates/chain-builder
• API reference (docs.rs) — https://docs.rs/chain-builder
• Source repository — https://github.com/AssetsArt/chain-builder
• CHANGELOG — https://github.com/AssetsArt/chain-builder/blob/main/CHANGELOG.md

This book is the long-form guide: query-building chapters, a reference section (binds, errors, sqlx execution, dialects), a cookbook of realistic recipes, and deep dives into the security model and compiler internals.