Bun provides native bindings for working with SQL databases through a unified Promise-based API that supports PostgreSQL, MySQL, and SQLite. The interface is designed to be simple and performant, using tagged template literals for queries and offering features like connection pooling, transactions, and prepared statements.

```ts
import { sql, SQL } from "bun";

// PostgreSQL (default)
const users = await sql`
  SELECT * FROM users
  WHERE active = ${true}
  LIMIT ${10}
`;

// With MySQL
const mysql = new SQL("mysql://user:pass@localhost:3306/mydb");
const mysqlResults = await mysql`
  SELECT * FROM users 
  WHERE active = ${true}
`;

// With SQLite
const sqlite = new SQL("sqlite://myapp.db");
const sqliteResults = await sqlite`
  SELECT * FROM users 
  WHERE active = ${1}
`;
```

{% features title="Features" %}

{% icon size=20 name="Shield" /%} Tagged template literals to protect against SQL injection

{% icon size=20 name="GitMerge" /%} Transactions

{% icon size=20 name="Variable" /%} Named & positional parameters

{% icon size=20 name="Network" /%} Connection pooling

{% icon size=20 name="Binary" /%} `BigInt` support

{% icon size=20 name="Key" /%} SASL Auth support (SCRAM-SHA-256), MD5, and Clear Text

{% icon size=20 name="Timer" /%} Connection timeouts

{% icon size=20 name="Database" /%} Returning rows as data objects, arrays of arrays, or `Buffer`

{% icon size=20 name="Code" /%} Binary protocol support makes it faster

{% icon size=20 name="Lock" /%} TLS support (and auth mode)

{% icon size=20 name="Settings" /%} Automatic configuration with environment variable

{% /features %}

## Database Support

Bun.SQL provides a unified API for multiple database systems:

### PostgreSQL

PostgreSQL is used when:

- The connection string doesn't match SQLite or MySQL patterns (it's the fallback adapter)
- The connection string explicitly uses `postgres://` or `postgresql://` protocols
- No connection string is provided and environment variables point to PostgreSQL

```ts
import { sql } from "bun";
// Uses PostgreSQL if DATABASE_URL is not set or is a PostgreSQL URL
await sql`SELECT ...`;

import { SQL } from "bun";
const pg = new SQL("postgres://user:pass@localhost:5432/mydb");
await pg`SELECT ...`;
```

### MySQL

MySQL support is built into Bun.SQL, providing the same tagged template literal interface with full compatibility for MySQL 5.7+ and MySQL 8.0+:

```ts
import { SQL } from "bun";

// MySQL connection
const mysql = new SQL("mysql://user:password@localhost:3306/database");
const mysql2 = new SQL("mysql2://user:password@localhost:3306/database"); // mysql2 protocol also works

// Using options object
const mysql3 = new SQL({
  adapter: "mysql",
  hostname: "localhost",
  port: 3306,
  database: "myapp",
  username: "dbuser",
  password: "secretpass",
});

// Works with parameters - automatically uses prepared statements
const users = await mysql`SELECT * FROM users WHERE id = ${userId}`;

// Transactions work the same as PostgreSQL
await mysql.begin(async tx => {
  await tx`INSERT INTO users (name) VALUES (${"Alice"})`;
  await tx`UPDATE accounts SET balance = balance - 100 WHERE user_id = ${userId}`;
});

// Bulk inserts
const newUsers = [
  { name: "Alice", email: "alice@example.com" },
  { name: "Bob", email: "bob@example.com" },
];
await mysql`INSERT INTO users ${mysql(newUsers)}`;
```

{% details summary="MySQL Connection String Formats" %}

MySQL accepts various URL formats for connection strings:

```ts
// Standard mysql:// protocol
new SQL("mysql://user:pass@localhost:3306/database");
new SQL("mysql://user:pass@localhost/database"); // Default port 3306

// mysql2:// protocol (compatibility with mysql2 npm package)
new SQL("mysql2://user:pass@localhost:3306/database");

// With query parameters
new SQL("mysql://user:pass@localhost/db?ssl=true");

// Unix socket connection
new SQL("mysql://user:pass@/database?socket=/var/run/mysqld/mysqld.sock");
```

{% /details %}

{% details summary="MySQL-Specific Features" %}

MySQL databases support:

- **Prepared statements**: Automatically created for parameterized queries with statement caching
- **Binary protocol**: For better performance with prepared statements and accurate type handling
- **Multiple result sets**: Support for stored procedures returning multiple result sets
- **Authentication plugins**: Support for mysql_native_password, caching_sha2_password (MySQL 8.0 default), and sha256_password
- **SSL/TLS connections**: Configurable SSL modes similar to PostgreSQL
- **Connection attributes**: Client information sent to server for monitoring
- **Query pipelining**: Execute multiple prepared statements without waiting for responses

{% /details %}

### SQLite

SQLite support is built into Bun.SQL, providing the same tagged template literal interface:

```ts
import { SQL } from "bun";

// In-memory database
const memory = new SQL(":memory:");
const memory2 = new SQL("sqlite://:memory:");

// File-based database
const db = new SQL("sqlite://myapp.db");

// Using options object
const db2 = new SQL({
  adapter: "sqlite",
  filename: "./data/app.db",
});

// For simple filenames, specify adapter explicitly
const db3 = new SQL("myapp.db", { adapter: "sqlite" });
```

{% details summary="SQLite Connection String Formats" %}

SQLite accepts various URL formats for connection strings:

```ts
// Standard sqlite:// protocol
new SQL("sqlite://path/to/database.db");
new SQL("sqlite:path/to/database.db"); // Without slashes

// file:// protocol (also recognized as SQLite)
new SQL("file://path/to/database.db");
new SQL("file:path/to/database.db");

// Special :memory: database
new SQL(":memory:");
new SQL("sqlite://:memory:");
new SQL("file://:memory:");

// Relative and absolute paths
new SQL("sqlite://./local.db"); // Relative to current directory
new SQL("sqlite://../parent/db.db"); // Parent directory
new SQL("sqlite:///absolute/path.db"); // Absolute path

// With query parameters
new SQL("sqlite://data.db?mode=ro"); // Read-only mode
new SQL("sqlite://data.db?mode=rw"); // Read-write mode (no create)
new SQL("sqlite://data.db?mode=rwc"); // Read-write-create mode (default)
```

**Note:** Simple filenames without a protocol (like `"myapp.db"`) require explicitly specifying `{ adapter: "sqlite" }` to avoid ambiguity with PostgreSQL.

{% /details %}

{% details summary="SQLite-Specific Options" %}

SQLite databases support additional configuration options:

```ts
const db = new SQL({
  adapter: "sqlite",
  filename: "app.db",

  // SQLite-specific options
  readonly: false, // Open in read-only mode
  create: true, // Create database if it doesn't exist
  readwrite: true, // Open for reading and writing

  // Additional Bun:sqlite options
  strict: true, // Enable strict mode
  safeIntegers: false, // Use JavaScript numbers for integers
});
```

Query parameters in the URL are parsed to set these options:

- `?mode=ro` → `readonly: true`
- `?mode=rw` → `readonly: false, create: false`
- `?mode=rwc` → `readonly: false, create: true` (default)

{% /details %}

### Inserting data

You can pass JavaScript values directly to the SQL template literal and escaping will be handled for you.

```ts
import { sql } from "bun";

// Basic insert with direct values
const [user] = await sql`
  INSERT INTO users (name, email) 
  VALUES (${name}, ${email})
  RETURNING *
`;

// Using object helper for cleaner syntax
const userData = {
  name: "Alice",
  email: "alice@example.com",
};

const [newUser] = await sql`
  INSERT INTO users ${sql(userData)}
  RETURNING *
`;
// Expands to: INSERT INTO users (name, email) VALUES ('Alice', 'alice@example.com')
```

### Bulk Insert

You can also pass arrays of objects to the SQL template literal and it will be expanded to a `INSERT INTO ... VALUES ...` statement.

```ts
const users = [
  { name: "Alice", email: "alice@example.com" },
  { name: "Bob", email: "bob@example.com" },
  { name: "Charlie", email: "charlie@example.com" },
];

await sql`INSERT INTO users ${sql(users)}`;
```

### Picking columns to insert

You can use `sql(object, ...string)` to pick which columns to insert. Each of the columns must be defined on the object.

```ts
const user = {
  name: "Alice",
  email: "alice@example.com",
  age: 25,
};

await sql`INSERT INTO users ${sql(user, "name", "email")}`;
// Only inserts name and email columns, ignoring other fields
```

## Query Results

By default, Bun's SQL client returns query results as arrays of objects, where each object represents a row with column names as keys. However, there are cases where you might want the data in a different format. The client provides two additional methods for this purpose.

### `sql``.values()` format

The `sql``.values()` method returns rows as arrays of values rather than objects. Each row becomes an array where the values are in the same order as the columns in your query.

```ts
const rows = await sql`SELECT * FROM users`.values();
console.log(rows);
```

This returns something like:

```ts
[
  ["Alice", "alice@example.com"],
  ["Bob", "bob@example.com"],
];
```

`sql``.values()` is especially useful if duplicate column names are returned in the query results. When using objects (the default), the last column name is used as the key in the object, which means duplicate column names overwrite each other &mdash; but when using `sql``.values()`, each column is present in the array so you can access the values of duplicate columns by index.

### `sql``.raw()` format

The `.raw()` method returns rows as arrays of `Buffer` objects. This can be useful for working with binary data or for performance reasons.

```ts
const rows = await sql`SELECT * FROM users`.raw();
console.log(rows); // [[Buffer, Buffer], [Buffer, Buffer], [Buffer, Buffer]]
```

## SQL Fragments

A common need in database applications is the ability to construct queries dynamically based on runtime conditions. Bun provides safe ways to do this without risking SQL injection.

### Dynamic Table Names

When you need to reference tables or schemas dynamically, use the `sql()` helper to ensure proper escaping:

```ts
// Safely reference tables dynamically
await sql`SELECT * FROM ${sql("users")}`;

// With schema qualification
await sql`SELECT * FROM ${sql("public.users")}`;
```

### Conditional Queries

You can use the `sql()` helper to build queries with conditional clauses. This allows you to create flexible queries that adapt to your application's needs:

```ts
// Optional WHERE clauses
const filterAge = true;
const minAge = 21;
const ageFilter = sql`AND age > ${minAge}`;
await sql`
  SELECT * FROM users
  WHERE active = ${true}
  ${filterAge ? ageFilter : sql``}
`;
```

### Dynamic columns in updates

You can use `sql(object, ...string)` to pick which columns to update. Each of the columns must be defined on the object. If the columns are not informed all keys will be used to update the row.

```ts
await sql`UPDATE users SET ${sql(user, "name", "email")} WHERE id = ${user.id}`;
// uses all keys from the object to update the row
await sql`UPDATE users SET ${sql(user)} WHERE id = ${user.id}`;
```

### Dynamic values and `where in`

Value lists can also be created dynamically, making where in queries simple too. Optionally you can pass a array of objects and inform what key to use to create the list.

```ts
await sql`SELECT * FROM users WHERE id IN ${sql([1, 2, 3])}`;

const users = [
  { id: 1, name: "Alice" },
  { id: 2, name: "Bob" },
  { id: 3, name: "Charlie" },
];
await sql`SELECT * FROM users WHERE id IN ${sql(users, "id")}`;
```

### `sql.array` helper

The `sql.array` helper creates PostgreSQL array literals from JavaScript arrays:

```ts
// Create array literals for PostgreSQL
await sql`INSERT INTO tags (items) VALUES (${sql.array(["red", "blue", "green"])})`;
// Generates: INSERT INTO tags (items) VALUES (ARRAY['red', 'blue', 'green'])

// Works with numeric arrays too
await sql`SELECT * FROM products WHERE ids = ANY(${sql.array([1, 2, 3])})`;
// Generates: SELECT * FROM products WHERE ids = ANY(ARRAY[1, 2, 3])
```

**Note**: `sql.array` is PostgreSQL-only. Multi-dimensional arrays and NULL elements may not be supported yet.

## `sql``.simple()`

The PostgreSQL wire protocol supports two types of queries: "simple" and "extended". Simple queries can contain multiple statements but don't support parameters, while extended queries (the default) support parameters but only allow one statement.

To run multiple statements in a single query, use `sql``.simple()`:

```ts
// Multiple statements in one query
await sql`
  SELECT 1;
  SELECT 2;
`.simple();
```

Simple queries are often useful for database migrations and setup scripts.

Note that simple queries cannot use parameters (`${value}`). If you need parameters, you must split your query into separate statements.

### Queries in files

You can use the `sql.file` method to read a query from a file and execute it, if the file includes $1, $2, etc you can pass parameters to the query. If no parameters are used it can execute multiple commands per file.

```ts
const result = await sql.file("query.sql", [1, 2, 3]);
```

### Unsafe Queries

You can use the `sql.unsafe` function to execute raw SQL strings. Use this with caution, as it will not escape user input. Executing more than one command per query is allowed if no parameters are used.

```ts
// Multiple commands without parameters
const result = await sql.unsafe(`
  SELECT ${userColumns} FROM users;
  SELECT ${accountColumns} FROM accounts;
`);

// Using parameters (only one command is allowed)
const result = await sql.unsafe(
  "SELECT " + dangerous + " FROM users WHERE id = $1",
  [id],
);
```

#### What is SQL Injection?

{% image href="https://xkcd.com/327/" src="https://imgs.xkcd.com/comics/exploits_of_a_mom.png" /%}

### Execute and Cancelling Queries

Bun's SQL is lazy, which means it will only start executing when awaited or executed with `.execute()`.
You can cancel a query that is currently executing by calling the `cancel()` method on the query object.

```ts
const query = await sql`SELECT * FROM users`.execute();
setTimeout(() => query.cancel(), 100);
await query;
```

## Database Environment Variables

`sql` connection parameters can be configured using environment variables. The client checks these variables in a specific order of precedence and automatically detects the database type based on the connection string format.

### Automatic Database Detection

When using `Bun.sql()` without arguments or `new SQL()` with a connection string, the adapter is automatically detected based on the URL format:

#### MySQL Auto-Detection

MySQL is automatically selected when the connection string matches these patterns:

- `mysql://...` - MySQL protocol URLs
- `mysql2://...` - MySQL2 protocol URLs (compatibility alias)

```ts
// These all use MySQL automatically (no adapter needed)
const sql1 = new SQL("mysql://user:pass@localhost/mydb");
const sql2 = new SQL("mysql2://user:pass@localhost:3306/mydb");

// Works with DATABASE_URL environment variable
DATABASE_URL="mysql://user:pass@localhost/mydb" bun run app.js
DATABASE_URL="mysql2://user:pass@localhost:3306/mydb" bun run app.js
```

#### SQLite Auto-Detection

SQLite is automatically selected when the connection string matches these patterns:

- `:memory:` - In-memory database
- `sqlite://...` - SQLite protocol URLs
- `sqlite:...` - SQLite protocol without slashes
- `file://...` - File protocol URLs
- `file:...` - File protocol without slashes

```ts
// These all use SQLite automatically (no adapter needed)
const sql1 = new SQL(":memory:");
const sql2 = new SQL("sqlite://app.db");
const sql3 = new SQL("file://./database.db");

// Works with DATABASE_URL environment variable
DATABASE_URL=":memory:" bun run app.js
DATABASE_URL="sqlite://myapp.db" bun run app.js
DATABASE_URL="file://./data/app.db" bun run app.js
```

#### PostgreSQL Auto-Detection

PostgreSQL is the default for connection strings that don't match MySQL or SQLite patterns:

```bash
# PostgreSQL is detected for these patterns
DATABASE_URL="postgres://user:pass@localhost:5432/mydb" bun run app.js
DATABASE_URL="postgresql://user:pass@localhost:5432/mydb" bun run app.js

# Or any URL that doesn't match MySQL or SQLite patterns
DATABASE_URL="localhost:5432/mydb" bun run app.js
```

### MySQL Environment Variables

MySQL connections can be configured via environment variables:

```bash
# Primary connection URL (checked first)
MYSQL_URL="mysql://user:pass@localhost:3306/mydb"

# Alternative: DATABASE_URL with MySQL protocol
DATABASE_URL="mysql://user:pass@localhost:3306/mydb"
DATABASE_URL="mysql2://user:pass@localhost:3306/mydb"
```

If no connection URL is provided, MySQL checks these individual parameters:

| Environment Variable     | Default Value | Description                      |
| ------------------------ | ------------- | -------------------------------- |
| `MYSQL_HOST`             | `localhost`   | Database host                    |
| `MYSQL_PORT`             | `3306`        | Database port                    |
| `MYSQL_USER`             | `root`        | Database user                    |
| `MYSQL_PASSWORD`         | (empty)       | Database password                |
| `MYSQL_DATABASE`         | `mysql`       | Database name                    |
| `MYSQL_URL`              | (empty)       | Primary connection URL for MySQL |
| `TLS_MYSQL_DATABASE_URL` | (empty)       | SSL/TLS-enabled connection URL   |

### PostgreSQL Environment Variables

The following environment variables can be used to define the PostgreSQL connection:

| Environment Variable        | Description                                |
| --------------------------- | ------------------------------------------ |
| `POSTGRES_URL`              | Primary connection URL for PostgreSQL      |
| `DATABASE_URL`              | Alternative connection URL (auto-detected) |
| `PGURL`                     | Alternative connection URL                 |
| `PG_URL`                    | Alternative connection URL                 |
| `TLS_POSTGRES_DATABASE_URL` | SSL/TLS-enabled connection URL             |
| `TLS_DATABASE_URL`          | Alternative SSL/TLS-enabled connection URL |

If no connection URL is provided, the system checks for the following individual parameters:

| Environment Variable | Fallback Variables           | Default Value | Description       |
| -------------------- | ---------------------------- | ------------- | ----------------- |
| `PGHOST`             | -                            | `localhost`   | Database host     |
| `PGPORT`             | -                            | `5432`        | Database port     |
| `PGUSERNAME`         | `PGUSER`, `USER`, `USERNAME` | `postgres`    | Database user     |
| `PGPASSWORD`         | -                            | (empty)       | Database password |
| `PGDATABASE`         | -                            | username      | Database name     |

### SQLite Environment Variables

SQLite connections can be configured via `DATABASE_URL` when it contains a SQLite-compatible URL:

```bash
# These are all recognized as SQLite
DATABASE_URL=":memory:"
DATABASE_URL="sqlite://./app.db"
DATABASE_URL="file:///absolute/path/to/db.sqlite"
```

**Note:** PostgreSQL-specific environment variables (`POSTGRES_URL`, `PGHOST`, etc.) are ignored when using SQLite.

## Runtime Preconnection

Bun can preconnect to PostgreSQL at startup to improve performance by establishing database connections before your application code runs. This is useful for reducing connection latency on the first database query.

```bash
# Enable PostgreSQL preconnection
bun --sql-preconnect index.js

# Works with DATABASE_URL environment variable
DATABASE_URL=postgres://user:pass@localhost:5432/db bun --sql-preconnect index.js

# Can be combined with other runtime flags
bun --sql-preconnect --hot index.js
```

The `--sql-preconnect` flag will automatically establish a PostgreSQL connection using your configured environment variables at startup. If the connection fails, it won't crash your application - the error will be handled gracefully.

## Connection Options

You can configure your database connection manually by passing options to the SQL constructor. Options vary depending on the database adapter:

### MySQL Options

```ts
import { SQL } from "bun";

const db = new SQL({
  // Required for MySQL when using options object
  adapter: "mysql",

  // Connection details
  hostname: "localhost",
  port: 3306,
  database: "myapp",
  username: "dbuser",
  password: "secretpass",

  // Unix socket connection (alternative to hostname/port)
  // socket: "/var/run/mysqld/mysqld.sock",

  // Connection pool settings
  max: 20, // Maximum connections in pool (default: 10)
  idleTimeout: 30, // Close idle connections after 30s
  maxLifetime: 0, // Connection lifetime in seconds (0 = forever)
  connectionTimeout: 30, // Timeout when establishing new connections

  // SSL/TLS options
  tls: {
    rejectUnauthorized: true,
    ca: "path/to/ca.pem",
    key: "path/to/key.pem",
    cert: "path/to/cert.pem",
  },

  // Callbacks
  onconnect: client => {
    console.log("Connected to MySQL");
  },
  onclose: (client, err) => {
    if (err) {
      console.error("MySQL connection error:", err);
    } else {
      console.log("MySQL connection closed");
    }
  },
});
```

### PostgreSQL Options

```ts
import { SQL } from "bun";

const db = new SQL({
  // Connection details (adapter is auto-detected as PostgreSQL)
  url: "postgres://user:pass@localhost:5432/dbname",

  // Alternative connection parameters
  hostname: "localhost",
  port: 5432,
  database: "myapp",
  username: "dbuser",
  password: "secretpass",

  // Connection pool settings
  max: 20, // Maximum connections in pool
  idleTimeout: 30, // Close idle connections after 30s
  maxLifetime: 0, // Connection lifetime in seconds (0 = forever)
  connectionTimeout: 30, // Timeout when establishing new connections

  // SSL/TLS options
  tls: true,
  // tls: {
  //   rejectUnauthorized: true,
  //   requestCert: true,
  //   ca: "path/to/ca.pem",
  //   key: "path/to/key.pem",
  //   cert: "path/to/cert.pem",
  //   checkServerIdentity(hostname, cert) {
  //     ...
  //   },
  // },

  // Callbacks
  onconnect: client => {
    console.log("Connected to PostgreSQL");
  },
  onclose: client => {
    console.log("PostgreSQL connection closed");
  },
});
```

### SQLite Options

```ts
import { SQL } from "bun";

const db = new SQL({
  // Required for SQLite
  adapter: "sqlite",
  filename: "./data/app.db", // or ":memory:" for in-memory database

  // SQLite-specific access modes
  readonly: false, // Open in read-only mode
  create: true, // Create database if it doesn't exist
  readwrite: true, // Allow read and write operations

  // SQLite data handling
  strict: true, // Enable strict mode for better type safety
  safeIntegers: false, // Use BigInt for integers exceeding JS number range

  // Callbacks
  onconnect: client => {
    console.log("SQLite database opened");
  },
  onclose: client => {
    console.log("SQLite database closed");
  },
});
```

{% details summary="SQLite Connection Notes" %}

- **Connection Pooling**: SQLite doesn't use connection pooling as it's a file-based database. Each `SQL` instance represents a single connection.
- **Transactions**: SQLite supports nested transactions through savepoints, similar to PostgreSQL.
- **Concurrent Access**: SQLite handles concurrent access through file locking. Use WAL mode for better concurrency.
- **Memory Databases**: Using `:memory:` creates a temporary database that exists only for the connection lifetime.

{% /details %}

## Dynamic passwords

When clients need to use alternative authentication schemes such as access tokens or connections to databases with rotating passwords, provide either a synchronous or asynchronous function that will resolve the dynamic password value at connection time.

```ts
import { SQL } from "bun";

const sql = new SQL(url, {
  // Other connection config
  ...
  // Password function for the database user
  password: async () => await signer.getAuthToken(),
});
```

## SQLite-Specific Features

### Query Execution

SQLite executes queries synchronously, unlike PostgreSQL which uses asynchronous I/O. However, the API remains consistent using Promises:

```ts
const sqlite = new SQL("sqlite://app.db");

// Works the same as PostgreSQL, but executes synchronously under the hood
const users = await sqlite`SELECT * FROM users`;

// Parameters work identically
const user = await sqlite`SELECT * FROM users WHERE id = ${userId}`;
```

### SQLite Pragmas

You can use PRAGMA statements to configure SQLite behavior:

```ts
const sqlite = new SQL("sqlite://app.db");

// Enable foreign keys
await sqlite`PRAGMA foreign_keys = ON`;

// Set journal mode to WAL for better concurrency
await sqlite`PRAGMA journal_mode = WAL`;

// Check integrity
const integrity = await sqlite`PRAGMA integrity_check`;
```

### Data Type Differences

SQLite has a more flexible type system than PostgreSQL:

```ts
// SQLite stores data in 5 storage classes: NULL, INTEGER, REAL, TEXT, BLOB
const sqlite = new SQL("sqlite://app.db");

// SQLite is more lenient with types
await sqlite`
  CREATE TABLE flexible (
    id INTEGER PRIMARY KEY,
    data TEXT,        -- Can store numbers as strings
    value NUMERIC,    -- Can store integers, reals, or text
    blob BLOB         -- Binary data
  )
`;

// JavaScript values are automatically converted
await sqlite`INSERT INTO flexible VALUES (${1}, ${"text"}, ${123.45}, ${Buffer.from("binary")})`;
```

## Transactions

To start a new transaction, use `sql.begin`. This method works for both PostgreSQL and SQLite. For PostgreSQL, it reserves a dedicated connection from the pool. For SQLite, it begins a transaction on the single connection.

The `BEGIN` command is sent automatically, including any optional configurations you specify. If an error occurs during the transaction, a `ROLLBACK` is triggered to ensure the process continues smoothly.

### Basic Transactions

```ts
await sql.begin(async tx => {
  // All queries in this function run in a transaction
  await tx`INSERT INTO users (name) VALUES (${"Alice"})`;
  await tx`UPDATE accounts SET balance = balance - 100 WHERE user_id = 1`;

  // Transaction automatically commits if no errors are thrown
  // Rolls back if any error occurs
});
```

It's also possible to pipeline the requests in a transaction if needed by returning an array with queries from the callback function like this:

```ts
await sql.begin(async tx => {
  return [
    tx`INSERT INTO users (name) VALUES (${"Alice"})`,
    tx`UPDATE accounts SET balance = balance - 100 WHERE user_id = 1`,
  ];
});
```

### Savepoints

Savepoints in SQL create intermediate checkpoints within a transaction, enabling partial rollbacks without affecting the entire operation. They are useful in complex transactions, allowing error recovery and maintaining consistent results.

```ts
await sql.begin(async tx => {
  await tx`INSERT INTO users (name) VALUES (${"Alice"})`;

  await tx.savepoint(async sp => {
    // This part can be rolled back separately
    await sp`UPDATE users SET status = 'active'`;
    if (someCondition) {
      throw new Error("Rollback to savepoint");
    }
  });

  // Continue with transaction even if savepoint rolled back
  await tx`INSERT INTO audit_log (action) VALUES ('user_created')`;
});
```

### Distributed Transactions

Two-Phase Commit (2PC) is a distributed transaction protocol where Phase 1 has the coordinator preparing nodes by ensuring data is written and ready to commit, while Phase 2 finalizes with nodes either committing or rolling back based on the coordinator's decision. This process ensures data durability and proper lock management.

In PostgreSQL and MySQL, distributed transactions persist beyond their original session, allowing privileged users or coordinators to commit or rollback them later. This supports robust distributed transactions, recovery processes, and administrative operations.

Each database system implements distributed transactions differently:

PostgreSQL natively supports them through prepared transactions, while MySQL uses XA Transactions.

If any exceptions occur during the distributed transaction and aren't caught, the system will automatically rollback all changes. When everything proceeds normally, you maintain the flexibility to either commit or rollback the transaction later.

```ts
// Begin a distributed transaction
await sql.beginDistributed("tx1", async tx => {
  await tx`INSERT INTO users (name) VALUES (${"Alice"})`;
});

// Later, commit or rollback
await sql.commitDistributed("tx1");
// or
await sql.rollbackDistributed("tx1");
```

## Authentication

Bun supports SCRAM-SHA-256 (SASL), MD5, and Clear Text authentication. SASL is recommended for better security. Check [Postgres SASL Authentication](https://www.postgresql.org/docs/current/sasl-authentication.html) for more information.

### SSL Modes Overview

PostgreSQL supports different SSL/TLS modes to control how secure connections are established. These modes determine the behavior when connecting and the level of certificate verification performed.

```ts
const sql = new SQL({
  hostname: "localhost",
  username: "user",
  password: "password",
  ssl: "disable", // | "prefer" | "require" | "verify-ca" | "verify-full"
});
```

| SSL Mode      | Description                                                                                                          |
| ------------- | -------------------------------------------------------------------------------------------------------------------- |
| `disable`     | No SSL/TLS used. Connections fail if server requires SSL.                                                            |
| `prefer`      | Tries SSL first, falls back to non-SSL if SSL fails. Default mode if none specified.                                 |
| `require`     | Requires SSL without certificate verification. Fails if SSL cannot be established.                                   |
| `verify-ca`   | Verifies server certificate is signed by trusted CA. Fails if verification fails.                                    |
| `verify-full` | Most secure mode. Verifies certificate and hostname match. Protects against untrusted certificates and MITM attacks. |

### Using With Connection Strings

The SSL mode can also be specified in connection strings:

```ts
// Using prefer mode
const sql = new SQL("postgres://user:password@localhost/mydb?sslmode=prefer");

// Using verify-full mode
const sql = new SQL(
  "postgres://user:password@localhost/mydb?sslmode=verify-full",
);
```

## Connection Pooling

Bun's SQL client automatically manages a connection pool, which is a pool of database connections that are reused for multiple queries. This helps to reduce the overhead of establishing and closing connections for each query, and it also helps to manage the number of concurrent connections to the database.

```ts
const db = new SQL({
  // Pool configuration
  max: 20, // Maximum 20 concurrent connections
  idleTimeout: 30, // Close idle connections after 30s
  maxLifetime: 3600, // Max connection lifetime 1 hour
  connectionTimeout: 10, // Connection timeout 10s
});
```

No connection will be made until a query is made.

```ts
const sql = Bun.sql(); // no connection are created

await sql`...`; // pool is started until max is reached (if possible), first available connection is used
await sql`...`; // previous connection is reused

// two connections are used now at the same time
await Promise.all([
  sql`INSERT INTO users ${sql({ name: "Alice" })}`,
  sql`UPDATE users SET name = ${user.name} WHERE id = ${user.id}`,
]);

await sql.close(); // await all queries to finish and close all connections from the pool
await sql.close({ timeout: 5 }); // wait 5 seconds and close all connections from the pool
await sql.close({ timeout: 0 }); // close all connections from the pool immediately
```

## Reserved Connections

Bun enables you to reserve a connection from the pool, and returns a client that wraps the single connection. This can be used for running queries on an isolated connection.

```ts
// Get exclusive connection from pool
const reserved = await sql.reserve();

try {
  await reserved`INSERT INTO users (name) VALUES (${"Alice"})`;
} finally {
  // Important: Release connection back to pool
  reserved.release();
}

// Or using Symbol.dispose
{
  using reserved = await sql.reserve();
  await reserved`SELECT 1`;
} // Automatically released
```

## Prepared Statements

By default, Bun's SQL client automatically creates named prepared statements for queries where it can be inferred that the query is static. This provides better performance. However, you can change this behavior by setting `prepare: false` in the connection options:

```ts
const sql = new SQL({
  // ... other options ...
  prepare: false, // Disable persisting named prepared statements on the server
});
```

When `prepare: false` is set:

Queries are still executed using the "extended" protocol, but they are executed using [unnamed prepared statements](https://www.postgresql.org/docs/current/protocol-flow.html#PROTOCOL-FLOW-EXT-QUERY), an unnamed prepared statement lasts only until the next Parse statement specifying the unnamed statement as destination is issued.

- Parameter binding is still safe against SQL injection
- Each query is parsed and planned from scratch by the server
- Queries will not be [pipelined](https://www.postgresql.org/docs/current/protocol-flow.html#PROTOCOL-FLOW-PIPELINING)

You might want to use `prepare: false` when:

- Using PGBouncer in transaction mode (though since PGBouncer 1.21.0, protocol-level named prepared statements are supported when configured properly)
- Debugging query execution plans
- Working with dynamic SQL where query plans need to be regenerated frequently
- More than one command per query will not be supported (unless you use `sql``.simple()`)

Note that disabling prepared statements may impact performance for queries that are executed frequently with different parameters, as the server needs to parse and plan each query from scratch.

## Error Handling

The client provides typed errors for different failure scenarios. Errors are database-specific and extend from base error classes:

### Error Classes

```ts
import { SQL } from "bun";

try {
  await sql`SELECT * FROM users`;
} catch (error) {
  if (error instanceof SQL.PostgresError) {
    // PostgreSQL-specific error
    console.log(error.code); // PostgreSQL error code
    console.log(error.detail); // Detailed error message
    console.log(error.hint); // Helpful hint from PostgreSQL
  } else if (error instanceof SQL.SQLiteError) {
    // SQLite-specific error
    console.log(error.code); // SQLite error code (e.g., "SQLITE_CONSTRAINT")
    console.log(error.errno); // SQLite error number
    console.log(error.byteOffset); // Byte offset in SQL statement (if available)
  } else if (error instanceof SQL.SQLError) {
    // Generic SQL error (base class)
    console.log(error.message);
  }
}
```

{% details summary="PostgreSQL-Specific Error Codes" %}

### PostgreSQL Connection Errors

| Connection Errors                 | Description                                          |
| --------------------------------- | ---------------------------------------------------- |
| `ERR_POSTGRES_CONNECTION_CLOSED`  | Connection was terminated or never established       |
| `ERR_POSTGRES_CONNECTION_TIMEOUT` | Failed to establish connection within timeout period |
| `ERR_POSTGRES_IDLE_TIMEOUT`       | Connection closed due to inactivity                  |
| `ERR_POSTGRES_LIFETIME_TIMEOUT`   | Connection exceeded maximum lifetime                 |
| `ERR_POSTGRES_TLS_NOT_AVAILABLE`  | SSL/TLS connection not available                     |
| `ERR_POSTGRES_TLS_UPGRADE_FAILED` | Failed to upgrade connection to SSL/TLS              |

### Authentication Errors

| Authentication Errors                            | Description                              |
| ------------------------------------------------ | ---------------------------------------- |
| `ERR_POSTGRES_AUTHENTICATION_FAILED_PBKDF2`      | Password authentication failed           |
| `ERR_POSTGRES_UNKNOWN_AUTHENTICATION_METHOD`     | Server requested unknown auth method     |
| `ERR_POSTGRES_UNSUPPORTED_AUTHENTICATION_METHOD` | Server requested unsupported auth method |
| `ERR_POSTGRES_INVALID_SERVER_KEY`                | Invalid server key during authentication |
| `ERR_POSTGRES_INVALID_SERVER_SIGNATURE`          | Invalid server signature                 |
| `ERR_POSTGRES_SASL_SIGNATURE_INVALID_BASE64`     | Invalid SASL signature encoding          |
| `ERR_POSTGRES_SASL_SIGNATURE_MISMATCH`           | SASL signature verification failed       |

### Query Errors

| Query Errors                         | Description                                |
| ------------------------------------ | ------------------------------------------ |
| `ERR_POSTGRES_SYNTAX_ERROR`          | Invalid SQL syntax (extends `SyntaxError`) |
| `ERR_POSTGRES_SERVER_ERROR`          | General error from PostgreSQL server       |
| `ERR_POSTGRES_INVALID_QUERY_BINDING` | Invalid parameter binding                  |
| `ERR_POSTGRES_QUERY_CANCELLED`       | Query was cancelled                        |
| `ERR_POSTGRES_NOT_TAGGED_CALL`       | Query was called without a tagged call     |

### Data Type Errors

| Data Type Errors                                        | Description                           |
| ------------------------------------------------------- | ------------------------------------- |
| `ERR_POSTGRES_INVALID_BINARY_DATA`                      | Invalid binary data format            |
| `ERR_POSTGRES_INVALID_BYTE_SEQUENCE`                    | Invalid byte sequence                 |
| `ERR_POSTGRES_INVALID_BYTE_SEQUENCE_FOR_ENCODING`       | Encoding error                        |
| `ERR_POSTGRES_INVALID_CHARACTER`                        | Invalid character in data             |
| `ERR_POSTGRES_OVERFLOW`                                 | Numeric overflow                      |
| `ERR_POSTGRES_UNSUPPORTED_BYTEA_FORMAT`                 | Unsupported binary format             |
| `ERR_POSTGRES_UNSUPPORTED_INTEGER_SIZE`                 | Integer size not supported            |
| `ERR_POSTGRES_MULTIDIMENSIONAL_ARRAY_NOT_SUPPORTED_YET` | Multidimensional arrays not supported |
| `ERR_POSTGRES_NULLS_IN_ARRAY_NOT_SUPPORTED_YET`         | NULL values in arrays not supported   |

### Protocol Errors

| Protocol Errors                         | Description                 |
| --------------------------------------- | --------------------------- |
| `ERR_POSTGRES_EXPECTED_REQUEST`         | Expected client request     |
| `ERR_POSTGRES_EXPECTED_STATEMENT`       | Expected prepared statement |
| `ERR_POSTGRES_INVALID_BACKEND_KEY_DATA` | Invalid backend key data    |
| `ERR_POSTGRES_INVALID_MESSAGE`          | Invalid protocol message    |
| `ERR_POSTGRES_INVALID_MESSAGE_LENGTH`   | Invalid message length      |
| `ERR_POSTGRES_UNEXPECTED_MESSAGE`       | Unexpected message type     |

### Transaction Errors

| Transaction Errors                       | Description                           |
| ---------------------------------------- | ------------------------------------- |
| `ERR_POSTGRES_UNSAFE_TRANSACTION`        | Unsafe transaction operation detected |
| `ERR_POSTGRES_INVALID_TRANSACTION_STATE` | Invalid transaction state             |

{% /details %}

### SQLite-Specific Errors

SQLite errors provide error codes and numbers that correspond to SQLite's standard error codes:

{% details summary="Common SQLite Error Codes" %}

| Error Code          | errno | Description                                          |
| ------------------- | ----- | ---------------------------------------------------- |
| `SQLITE_CONSTRAINT` | 19    | Constraint violation (UNIQUE, CHECK, NOT NULL, etc.) |
| `SQLITE_BUSY`       | 5     | Database is locked                                   |
| `SQLITE_LOCKED`     | 6     | Table in the database is locked                      |
| `SQLITE_READONLY`   | 8     | Attempt to write to a readonly database              |
| `SQLITE_IOERR`      | 10    | Disk I/O error                                       |
| `SQLITE_CORRUPT`    | 11    | Database disk image is malformed                     |
| `SQLITE_FULL`       | 13    | Database or disk is full                             |
| `SQLITE_CANTOPEN`   | 14    | Unable to open database file                         |
| `SQLITE_PROTOCOL`   | 15    | Database lock protocol error                         |
| `SQLITE_SCHEMA`     | 17    | Database schema has changed                          |
| `SQLITE_TOOBIG`     | 18    | String or BLOB exceeds size limit                    |
| `SQLITE_MISMATCH`   | 20    | Data type mismatch                                   |
| `SQLITE_MISUSE`     | 21    | Library used incorrectly                             |
| `SQLITE_AUTH`       | 23    | Authorization denied                                 |

Example error handling:

```ts
const sqlite = new SQL("sqlite://app.db");

try {
  await sqlite`INSERT INTO users (id, name) VALUES (1, 'Alice')`;
  await sqlite`INSERT INTO users (id, name) VALUES (1, 'Bob')`; // Duplicate ID
} catch (error) {
  if (error instanceof SQL.SQLiteError) {
    if (error.code === "SQLITE_CONSTRAINT") {
      console.log("Constraint violation:", error.message);
      // Handle unique constraint violation
    }
  }
}
```

{% /details %}

## Numbers and BigInt

Bun's SQL client includes special handling for large numbers that exceed the range of a 53-bit integer. Here's how it works:

```ts
import { sql } from "bun";

const [{ x, y }] = await sql`SELECT 9223372036854777 as x, 12345 as y`;

console.log(typeof x, x); // "string" "9223372036854777"
console.log(typeof y, y); // "number" 12345
```

## BigInt Instead of Strings

If you need large numbers as BigInt instead of strings, you can enable this by setting the `bigint` option to `true` when initializing the SQL client:

```ts
const sql = new SQL({
  bigint: true,
});

const [{ x }] = await sql`SELECT 9223372036854777 as x`;

console.log(typeof x, x); // "bigint" 9223372036854777n
```

## Roadmap

There's still some things we haven't finished yet.

- Connection preloading via `--db-preconnect` Bun CLI flag
- Column name transforms (e.g. `snake_case` to `camelCase`). This is mostly blocked on a unicode-aware implementation of changing the case in C++ using WebKit's `WTF::String`.
- Column type transforms

## Database-Specific Features

#### Authentication Methods

MySQL supports multiple authentication plugins that are automatically negotiated:

- **`mysql_native_password`** - Traditional MySQL authentication, widely compatible
- **`caching_sha2_password`** - Default in MySQL 8.0+, more secure with RSA key exchange
- **`sha256_password`** - SHA-256 based authentication

The client automatically handles authentication plugin switching when requested by the server, including secure password exchange over non-SSL connections.

#### Prepared Statements & Performance

MySQL uses server-side prepared statements for all parameterized queries:

```ts
// This automatically creates a prepared statement on the server
const user = await mysql`SELECT * FROM users WHERE id = ${userId}`;

// Prepared statements are cached and reused for identical queries
for (const id of userIds) {
  // Same prepared statement is reused
  await mysql`SELECT * FROM users WHERE id = ${id}`;
}

// Query pipelining - multiple statements sent without waiting
const [users, orders, products] = await Promise.all([
  mysql`SELECT * FROM users WHERE active = ${true}`,
  mysql`SELECT * FROM orders WHERE status = ${"pending"}`,
  mysql`SELECT * FROM products WHERE in_stock = ${true}`,
]);
```

#### Multiple Result Sets

MySQL can return multiple result sets from multi-statement queries:

```ts
const mysql = new SQL("mysql://user:pass@localhost/mydb");

// Multi-statement queries with simple() method
const multiResults = await mysql`
  SELECT * FROM users WHERE id = 1;
  SELECT * FROM orders WHERE user_id = 1;
`.simple();
```

#### Character Sets & Collations

Bun.SQL automatically uses `utf8mb4` character set for MySQL connections, ensuring full Unicode support including emojis. This is the recommended character set for modern MySQL applications.

#### Connection Attributes

Bun automatically sends client information to MySQL for better monitoring:

```ts
// These attributes are sent automatically:
// _client_name: "Bun"
// _client_version: <bun version>
// You can see these in MySQL's performance_schema.session_connect_attrs
```

#### Type Handling

MySQL types are automatically converted to JavaScript types:

| MySQL Type                              | JavaScript Type          | Notes                                                                                                |
| --------------------------------------- | ------------------------ | ---------------------------------------------------------------------------------------------------- |
| INT, TINYINT, MEDIUMINT                 | number                   | Within safe integer range                                                                            |
| BIGINT                                  | string, number or BigInt | If the value fits in i32/u32 size will be number otherwise string or BigInt Based on `bigint` option |
| DECIMAL, NUMERIC                        | string                   | To preserve precision                                                                                |
| FLOAT, DOUBLE                           | number                   |                                                                                                      |
| DATE                                    | Date                     | JavaScript Date object                                                                               |
| DATETIME, TIMESTAMP                     | Date                     | With timezone handling                                                                               |
| TIME                                    | number                   | Total of microseconds                                                                                |
| YEAR                                    | number                   |                                                                                                      |
| CHAR, VARCHAR, VARSTRING, STRING        | string                   |                                                                                                      |
| TINY TEXT, MEDIUM TEXT, TEXT, LONG TEXT | string                   |                                                                                                      |
| TINY BLOB, MEDIUM BLOB, BLOG, LONG BLOB | string                   | BLOB Types are alias for TEXT types                                                                  |
| JSON                                    | object/array             | Automatically parsed                                                                                 |
| BIT(1)                                  | boolean                  | BIT(1) in MySQL                                                                                      |
| GEOMETRY                                | string                   | Geometry data                                                                                        |

#### Differences from PostgreSQL

While the API is unified, there are some behavioral differences:

1. **Parameter placeholders**: MySQL uses `?` internally but Bun converts `$1, $2` style automatically
2. **RETURNING clause**: MySQL doesn't support RETURNING; use `result.lastInsertRowid` or a separate SELECT
3. **Array types**: MySQL doesn't have native array types like PostgreSQL

### MySQL-Specific Features

We haven't implemented `LOAD DATA INFILE` support yet

### PostgreSQL-Specific Features

We haven't implemented these yet:

- `COPY` support
- `LISTEN` support
- `NOTIFY` support

We also haven't implemented some of the more uncommon features like:

- GSSAPI authentication
- `SCRAM-SHA-256-PLUS` support
- Point & PostGIS types
- All the multi-dimensional integer array types (only a couple of the types are supported)

## Common Patterns & Best Practices

### Working with MySQL Result Sets

```ts
// Getting insert ID after INSERT
const result = await mysql`INSERT INTO users (name) VALUES (${"Alice"})`;
console.log(result.lastInsertRowid); // MySQL's LAST_INSERT_ID()

// Handling affected rows
const updated =
  await mysql`UPDATE users SET active = ${false} WHERE age < ${18}`;
console.log(updated.affectedRows); // Number of rows updated

// Using MySQL-specific functions
const now = await mysql`SELECT NOW() as current_time`;
const uuid = await mysql`SELECT UUID() as id`;
```

### MySQL Error Handling

```ts
try {
  await mysql`INSERT INTO users (email) VALUES (${"duplicate@email.com"})`;
} catch (error) {
  if (error.code === "ER_DUP_ENTRY") {
    console.log("Duplicate entry detected");
  } else if (error.code === "ER_ACCESS_DENIED_ERROR") {
    console.log("Access denied");
  } else if (error.code === "ER_BAD_DB_ERROR") {
    console.log("Database does not exist");
  }
  // MySQL error codes are compatible with mysql/mysql2 packages
}
```

### Performance Tips for MySQL

1. **Use connection pooling**: Set appropriate `max` pool size based on your workload
2. **Enable prepared statements**: They're enabled by default and improve performance
3. **Use transactions for bulk operations**: Group related queries in transactions
4. **Index properly**: MySQL relies heavily on indexes for query performance
5. **Use `utf8mb4` charset**: It's set by default and handles all Unicode characters

## Frequently Asked Questions

> Why is this `Bun.sql` and not `Bun.postgres`?

The plan was to add more database drivers in the future. Now with MySQL support added, this unified API supports PostgreSQL, MySQL, and SQLite.

> How do I know which database adapter is being used?

The adapter is automatically detected from the connection string:

- URLs starting with `mysql://` or `mysql2://` use MySQL
- URLs matching SQLite patterns (`:memory:`, `sqlite://`, `file://`) use SQLite
- Everything else defaults to PostgreSQL

> Are MySQL stored procedures supported?

Yes, stored procedures are fully supported including OUT parameters and multiple result sets:

```ts
// Call stored procedure
const results = await mysql`CALL GetUserStats(${userId}, @total_orders)`;

// Get OUT parameter
const outParam = await mysql`SELECT @total_orders as total`;
```

> Can I use MySQL-specific SQL syntax?

Yes, you can use any MySQL-specific syntax:

```ts
// MySQL-specific syntax works fine
await mysql`SET @user_id = ${userId}`;
await mysql`SHOW TABLES`;
await mysql`DESCRIBE users`;
await mysql`EXPLAIN SELECT * FROM users WHERE id = ${id}`;
```

## Why not just use an existing library?

npm packages like postgres.js, pg, and node-postgres can be used in Bun too. They're great options.

Two reasons why:

1. We think it's simpler for developers to have a database driver built into Bun. The time you spend library shopping is time you could be building your app.
2. We leverage some JavaScriptCore engine internals to make it faster to create objects that would be difficult to implement in a library

## Credits

Huge thanks to [@porsager](https://github.com/porsager)'s [postgres.js](https://github.com/porsager/postgres) for the inspiration for the API interface.
