The Rust SQL Toolkit



The Rust SQL Toolkit. An async, pure Rust SQL crate featuring compile-time checked queries without a DSL. Supports PostgreSQL, MySQL, SQLite, and MSSQL.

SQLx is an async, pure Rust SQL crate featuring compile-time checked queries without a DSL.

  • Truly Asynchronous. Built from the ground-up using async/await for maximum concurrency.
  • Compile-time checked queries (if you want). See SQLx is not an ORM.
  • Database Agnostic. Support for PostgreSQLMySQLSQLite, and MSSQL.
  • Pure Rust. The Postgres and MySQL/MariaDB drivers are written in pure Rust using zero unsafe†† code.
  • Runtime Agnostic. Works on different runtimes (async-std / tokio / actix) and TLS backends (native-tlsrustls).

The SQLite driver uses the libsqlite3 C library as SQLite is an embedded database (the only way we could be pure Rust for SQLite is by porting all of SQLite to Rust).

†† SQLx uses #![forbid(unsafe_code)] unless the sqlite feature is enabled. As the SQLite driver interacts with C, those interactions are unsafe.

  • Cross-platform. Being native Rust, SQLx will compile anywhere Rust is supported.
  • Built-in connection pooling with sqlx::Pool.
  • Row streaming. Data is read asynchronously from the database and decoded on-demand.
  • Automatic statement preparation and caching. When using the high-level query API (sqlx::query), statements are prepared and cached per-connection.
  • Simple (unprepared) query execution including fetching results into the same Row types used by the high-level API. Supports batch execution and returning results from all statements.
  • Transport Layer Security (TLS) where supported (MySQL and PostgreSQL).
  • Asynchronous notifications using LISTEN and NOTIFY for PostgreSQL.
  • Nested transactions with support for save points.
  • Any database driver for changing the database driver at runtime. An AnyPool connects to the driver indicated by the URI scheme.


SQLx is compatible with the async-stdtokio and actix runtimes; and, the native-tls and rustls TLS backends. When adding the dependency, you must chose a runtime feature that is runtime + tls.

# Cargo.toml
# tokio + rustls
sqlx = { version = "0.5", features = [ "runtime-tokio-rustls" ] }
# async-std + native-tls
sqlx = { version = "0.5", features = [ "runtime-async-std-native-tls" ] }

The runtime and TLS backend not being separate feature sets to select is a workaround for a Cargo issue.

Cargo Feature Flags

  • runtime-async-std-native-tls: Use the async-std runtime and native-tls TLS backend.
  • runtime-async-std-rustls: Use the async-std runtime and rustls TLS backend.
  • runtime-tokio-native-tls: Use the tokio runtime and native-tls TLS backend.
  • runtime-tokio-rustls: Use the tokio runtime and rustls TLS backend.
  • runtime-actix-native-tls: Use the actix runtime and native-tls TLS backend.
  • runtime-actix-rustls: Use the actix runtime and rustls TLS backend.
  • postgres: Add support for the Postgres database server.
  • mysql: Add support for the MySQL/MariaDB database server.
  • mssql: Add support for the MSSQL database server.
  • sqlite: Add support for the self-contained SQLite database engine.
  • any: Add support for the Any database driver, which can proxy to a database driver at runtime.
  • macros: Add support for the query*! macros, which allow compile-time checked queries.
  • migrate: Add support for the migration management and migrate! macro, which allow compile-time embedded migrations.
  • uuid: Add support for UUID (in Postgres).
  • chrono: Add support for date and time types from chrono.
  • time: Add support for date and time types from time crate (alternative to chrono, which is preferred by query! macro, if both enabled)
  • bstr: Add support for bstr::BString.
  • git2: Add support for git2::Oid.
  • bigdecimal: Add support for NUMERIC using the bigdecimal crate.
  • decimal: Add support for NUMERIC using the rust_decimal crate.
  • ipnetwork: Add support for INET and CIDR (in postgres) using the ipnetwork crate.
  • json: Add support for JSON and JSONB (in postgres) using the serde_json crate.
  • tls: Add support for TLS connections.
  • offline: Enables building the macros in offline mode when a live database is not available (such as CI).
    • Requires sqlx-cli installed to use. See sqlx-cli/

SQLx is not an ORM!

SQLx supports compile-time checked queries. It does not, however, do this by providing a Rust API or DSL (domain-specific language) for building queries. Instead, it provides macros that take regular SQL as an input and ensure that it is valid for your database. The way this works is that SQLx connects to your development DB at compile time to have the database itself verify (and return some info on) your SQL queries. This has some potentially surprising implications:

  • Since SQLx never has to parse the SQL string itself, any syntax that the development DB accepts can be used (including things added by database extensions)
  • Due to the different amount of information databases let you retrieve about queries, the extent of SQL verification you get from the query macros depends on the database

If you are looking for an (asynchronous) ORM, you can check out ormx or SeaORM, which is built on top of SQLx.


See the examples/ folder for more in-depth usage.


# Async-std:
sqlx = { version = "0.5", features = [  "runtime-async-std-native-tls", "postgres" ] }
async-std = { version = "1", features = [ "attributes" ] }

# Tokio:
sqlx = { version = "0.5", features = [ "runtime-tokio-native-tls" , "postgres" ] }
tokio = { version = "1", features = ["full"] }

# Actix-web:
sqlx = { version = "0.5", features = [ "runtime-actix-native-tls" , "postgres" ] }
actix-web = "3"
use sqlx::postgres::PgPoolOptions;
// use sqlx::mysql::MySqlPoolOptions;
// etc.

// or #[tokio::main]
// or #[actix_web::main]
async fn main() -> Result<(), sqlx::Error> {
    // Create a connection pool
    //  for MySQL, use MySqlPoolOptions::new()
    //  for SQLite, use SqlitePoolOptions::new()
    //  etc.
    let pool = PgPoolOptions::new()

    // Make a simple query to return the given parameter (use a question mark `?` instead of `$1` for MySQL)
    let row: (i64,) = sqlx::query_as("SELECT $1")

    assert_eq!(row.0, 150);



A single connection can be established using any of the database connection types and calling connect().

use sqlx::Connection;

let conn = SqliteConnection::connect("sqlite::memory:").await?;

Generally, you will want to instead create a connection pool (sqlx::Pool) in order for your application to regulate how many server-side connections it’s using.

let pool = MySqlPool::connect("mysql://user:pass@host/database").await?;


In SQL, queries can be separated into prepared (parameterized) or unprepared (simple). Prepared queries have their query plan cached, use a binary mode of communication (lower bandwidth and faster decoding), and utilize parameters to avoid SQL injection. Unprepared queries are simple and intended only for use case where a prepared statement will not work, such as various database commands (e.g., PRAGMA or SET or BEGIN).

SQLx supports all operations with both types of queries. In SQLx, a &str is treated as an unprepared query and a Query or QueryAs struct is treated as a prepared query.

// low-level, Executor trait
conn.execute("BEGIN").await?; // unprepared, simple query
conn.execute(sqlx::query("DELETE FROM table")).await?; // prepared, cached query

We should prefer to use the high level, query interface whenever possible. To make this easier, there are finalizers on the type to avoid the need to wrap with an executor.

sqlx::query("DELETE FROM table").execute(&mut conn).await?;
sqlx::query("DELETE FROM table").execute(&pool).await?;

The execute query finalizer returns the number of affected rows, if any, and drops all received results. In addition, there are fetchfetch_onefetch_optional, and fetch_all to receive results.

The Query type returned from sqlx::query will return Row<'conn> from the database. Column values can be accessed by ordinal or by name with row.get(). As the Row retains an immutable borrow on the connection, only one Row may exist at a time.

The fetch query finalizer returns a stream-like type that iterates through the rows in the result sets.

// provides `try_next`
use futures::TryStreamExt;

let mut rows = sqlx::query("SELECT * FROM users WHERE email = ?")
    .fetch(&mut conn);

while let Some(row) = rows.try_next().await? {
    // map the row into a user-defined domain type
    let email: &str = row.try_get("email")?;

To assist with mapping the row into a domain type, there are two idioms that may be used:

let mut stream = sqlx::query("SELECT * FROM users")
    .map(|row: PgRow| {
        // map the row into a user-defined domain type
    .fetch(&mut conn);
struct User { name: String, id: i64 }

let mut stream = sqlx::query_as::<_, User>("SELECT * FROM users WHERE email = ? OR name = ?")
    .fetch(&mut conn);

Instead of a stream of results, we can use fetch_one or fetch_optional to request one required or optional result from the database.

Compile-time verification

We can use the macro, sqlx::query! to achieve compile-time syntactic and semantic verification of the SQL, with an output to an anonymous record type where each SQL column is a Rust field (using raw identifiers where needed).

let countries = sqlx::query!(
SELECT country, COUNT(*) as count
FROM users
GROUP BY country
WHERE organization = ?
    .fetch_all(&pool) // -> Vec<{ country: String, count: i64 }>

// countries[0].country
// countries[0].count

Differences from query():

  • The input (or bind) parameters must be given all at once (and they are compile-time validated to be the right number and the right type).
  • The output type is an anonymous record. In the above example the type would be similar to:
{ country: String, count: i64 }
  • The DATABASE_URL environment variable must be set at build time to a database which it can prepare queries against; the database does not have to contain any data but must be the same kind (MySQL, Postgres, etc.) and have the same schema as the database you will be connecting to at runtime.For convenience, you can use a .env file to set DATABASE_URL so that you don’t have to pass it every time:

The biggest downside to query!() is that the output type cannot be named (due to Rust not officially supporting anonymous records). To address that, there is a query_as!() macro that is mostly identical except that you can name the output type.

// no traits are needed
struct Country { country: String, count: i64 }

let countries = sqlx::query_as!(Country,
SELECT country, COUNT(*) as count
FROM users
GROUP BY country
WHERE organization = ?
    .fetch_all(&pool) // -> Vec<Country>

// countries[0].country
// countries[0].count

To avoid the need of having a development database around to compile the project even when no modifications (to the database-accessing parts of the code) are done, you can enable “offline mode” to cache the results of the SQL query analysis using the sqlx command-line tool. See sqlx-cli/

Compile time verified queries do quite a bit of work at compile time. Incremental actions like cargo check and cargo build can be significantly faster when using an optimized build by putting the following in your Cargo.toml (More information in the Profiles section of The Cargo Book)

opt-level = 3


This crate uses #![forbid(unsafe_code)] to ensure everything is implemented in 100% Safe Rust.

If the sqlite feature is enabled, this is downgraded to #![deny(unsafe_code)] with #![allow(unsafe_code)] on the sqlx::sqlite module. There are several places where we interact with the C SQLite API. We try to document each call for the invariants we’re assuming. We absolutely welcome auditing of, and feedback on, our unsafe code usage.

The SQLx is a github repository by launchbadge