An SQL query builder for sqlx. Work in progress
Suppose you have a table like this:
CREATE TABLE book(
id INTEGER PRIMARY KEY,
title TEXT NOT NULL,
author TEXT,
lang TEXT,
year SMALLINT
);The CRUD (or ISUD with sql acronym) will be look like this:
let book1 = "The Fellowship of the Rings".to_string();
let auth1 = "J. R. R. Tolkien".to_string();
let book2 = "Dune".to_string();
let auth2 = "Frank Herbret".to_string();
let english = "English".to_string();
let values = [
(1_i32, &book1, &auth1, &english, 1954_i16),
(2_i32, &book2, &auth2, &english, 1965_i16),
];
let insert = xql::insert("book", ["id", "title", "author", "lang", "year"])
.values(values)
.returning(["id"]);
assert_eq!(
insert.to_string(),
"INSERT INTO book(id, title, author, lang, year) VALUES \
(1, 'The Fellowship of the Rings', 'J. R. R. Tolkien', 'English', 1954), \
(2, 'Dune', 'Frank Herbret', 'English', 1965) \
RETURNING id",
);let select = xql::select(["id", "title"])
.from("book")
.filter(xql::or(xql::eq("id", 1), xql::eq("id", 2)))
.order_by(xql::desc("year"));
assert_eq!(
select.to_string(),
"SELECT id, title FROM book WHERE id = 1 OR id = 2 ORDER BY year DESC"
);let author = &"Frank Herbert".to_string();
let update = xql::update("book")
.set("author", author)
.filter(xql::eq("id", 2))
.returning(["id"]);
assert_eq!(
update.to_string(),
"UPDATE book SET author = 'Frank Herbert' WHERE id = 2 RETURNING id",
);let delete = xql::delete("book")
.filter(xql::eq("id", 1))
.returning(["id", "title"]);
assert_eq!(
delete.to_string(),
"DELETE FROM book WHERE id = 1 RETURNING id, title",
);There are some blanket implementation for traits that defined
in xql::blanket to assist query building.
Most of expr's function defined in xql::ops have method of blanket
implementation of xql::blanket::ExprExt.
use xql::blanket::ExprExt;
let cond = "year".greater_than(1900).and("year".less_equal(2000));
assert_eq!(cond.to_string(), "year > 1900 AND year <= 2000");
let query = xql::select(["id"]).from("book").filter(cond);
assert_eq!(query.to_string(), "SELECT id FROM book WHERE year > 1900 AND year <= 2000");Well, that looks verbose. It can't be helped, because using gt or le will
clash with PartialOrd (which can't be disabled even with
no_implicit_prelude). This one below will not compile.
use xql::blanket::ExprExt;
let cond = "year".gt(1900).and("year".le(2000));A work around is to turn the left hand side into Expr first or using a table qualified
column reference.
use xql::expr::Expr;
use xql::blanket::ExprExt;
let year = Expr::from("year");
let qualified = ("book", "year");
let cond = year.gt(1900).and(qualified.le(2000));
assert_eq!(cond.to_string(), "year > 1900 AND book.year <= 2000");join family functions have some blanket implementations.
use xql::blanket::ExprExt;
use xql::blanket::TableExprExt;
let table = "book".join("category", ("book", "category_id").eq(("category", "id")));
assert_eq!(table.to_string(), "book JOIN category ON book.category_id = category.id");SELECT and VALUES are the only statements that can use UNION family functions.
use xql::blanket::ResultExt;
let query = xql::select([1, 2]).union(xql::values([(3, 4)]));
assert_eq!(query.to_string(), "SELECT 1, 2 UNION VALUES (3, 4)");In case you're wondering, ResultExt's name came from
xql::stmt::result::Result which is an enum of only Select and Values. Why
Result? Well, because naming is hard and it looks good in Stmt enum definition:
enum Stmt {
Insert,
Select,
Update,
Delete,
Values,
Binary,
Result, // See!? Exactly 6 characters! Perfectly balanced as all things should be!
}You can enable derive feature to make query building looks shorter or nicer.
use xql::Schema;
#[derive(Schema)]
struct Book {
id: i32,
title: String,
author: Option<String>,
lang: Option<String>,
year: Option<i32>,
}
let shorter = xql::select(Book::columns()).from(Book::table());
assert_eq!(shorter.to_string(), "SELECT book.id, book.title, book.author, book.lang, book.year FROM book");
let nicer = xql::select([Book::id, Book::title, Book::author, Book::lang, Book::year]).from(Book);
assert_eq!(nicer.to_string(), "SELECT book.id, book.title, book.author, book.lang, book.year FROM book");
assert_eq!(shorter, nicer);The table qualified column will turn to unqualified in INSERT's columns or
UPDATE's SET.
use xql::Schema;
use xql::blanket::ExprExt;
#[derive(Schema)]
struct Book {
id: i32,
title: String,
author: Option<String>,
lang: Option<String>,
year: Option<i32>,
}
let values = [(&"Dune".to_string(),)];
let insert = xql::insert(Book, [Book::title]).values(values);
assert_eq!(insert.to_string(), "INSERT INTO book(title) VALUES ('Dune')");
let author = "Frank Herbert".to_string();
let update = xql::update(Book).set(Book::author, &author).filter(Book::id.eq(2));
assert_eq!(update.to_string(), "UPDATE book SET author = 'Frank Herbert' WHERE book.id = 2");To execute those queries, enable sqlx feature and one of postgres, mysql
or sqlite feature.
#[derive(sqlx::FromRow)]
struct Output {
id: i32,
title: String,
}
#[cfg(feature = "postgres")]
async fn execute(pool: sqlx::Pool::<sqlx::Postgres>) -> Result<(), sqlx::Error> {
// sqlx::query(..).fetch_all
let query = xql::select(["id", "title"]).from("book");
let rows = xql::exec::fetch_all(query, &pool).await?;
// sqlx::query_as(..).fetch_all
let query = xql::select(["id", "title"]).from("book");
let rows: Vec<Output> = xql::exec::fetch_all_as(query, &pool).await?;
// sqlx::query_scalar(..).fetch_all
let query = xql::select(["id"]).from("book");
let rows: Vec<i32> = xql::exec::fetch_all_scalar(query, &pool).await?;
// or in blanket form
use xql::blanket::StmtExt;
let rows = xql::select(["id", "title"])
.from("book")
.fetch_all(&pool).await?;
let rows: Vec<Output> = xql::select(["id", "title"])
.from("book")
.fetch_all_as(&pool)
.await?;
let rows: Vec<i32> = xql::select(["id"])
.from("book")
.fetch_all_scalar(&pool).await?;
Ok(())
}Available variants are: fetch_one, fetch_all, fetch_optional with _as,
_scalar or no suffix respectively.
You may notice serveral use of &"text".to_string() in the examples above.
That's because &str will turn into an identifier while &String will turn
into a literal text.