typed-qb: a compile-time typed "query builder"

typed-qb is a compile-time, typed, query builder. The goal of this crate is to explore the gap between compile-time verification of raw SQL queries (like sqlx) and runtime generation of queries via query builders (like diesel).

The query is transformed into an SQL query string at compile time. If code compiles and the schema in the code matches the database, it should be (almost) impossible to write queries that produce errors.

Usage

You can specify your table structure by pasting the output of SHOW CREATE TABLE .. into the tables! macro. You will need to clean up the backticks (`), because Rust cannot parse them. For example:

tables! {
    CREATE TABLE Users (
        Id INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,
        Name VARCHAR(64) NOT NULL,
        PRIMARY KEY(Id)
    );
}

Field names will automatically be converted to snake_case if you write them in camelCase or PascalCase. You can then query the table as follows:

let conn = ...; // some connection

let all_users = conn.typed_query(
    Users::query(|user| data! {
        id: user.id,
        name: user.name,
    })
)?;

for user in all_users {
    let user = user?;
    println!("{} ({})", user.id, user.name);
}

The query is transformed at compile-time into:

SELECT `t0`.`Id` AS `id`, `t0`.`Name` AS `name` 
FROM `Users` AS t0

You can specify WHERE, ORDER BY, etc. clauses with the select function:

Users::query(|user| select(data! {
    id: user.id,
    name: user.name,
}, |selected| {
    expr!(selected.id < 5)
        .order_by(selected.name.asc()
            .then_by(selected.id.desc())
        )
        .limit::<3>()
}))

The type returned by typed_query depends on the query itself. The two queries above return an iterator over an anonymous struct. If a single value is selected, for example:

let user_count = conn.typed_query(Users::query(|_| expr!(COUNT(*))))?;

The type of user_count will be a u64.

See more examples.

(In)stability

This project requires Rust nightly, and uses a bunch of features, some incomplete. You might encounter ICEs. There will probably be many breaking changes to typed-qb itself as well. You probably shouldn't use typed-qb for serious projects.

License

typed-qb is licensed under the Mozilla Public License 2.0 (MPL2.0). See the LICENSE file.