Expand description
qians_xql
An SQL query builder for sqlx. Work in progress
Table of Contents
Basic Query Building
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:
INSERT
statement.
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 = qians_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",
);
SELECT
statement.
let select = qians_xql::select(["id", "title"])
.from("book")
.filter(qians_xql::or(qians_xql::eq("id", 1), qians_xql::eq("id", 2)))
.order_by(qians_xql::desc("year"));
assert_eq!(
select.to_string(),
"SELECT id, title FROM book WHERE id = 1 OR id = 2 ORDER BY year DESC"
);
UPDATE
statement.
let author = &"Frank Herbert".to_string();
let update = qians_xql::update("book")
.set("author", author)
.filter(qians_xql::eq("id", 2))
.returning(["id"]);
assert_eq!(
update.to_string(),
"UPDATE book SET author = 'Frank Herbert' WHERE id = 2 RETURNING id",
);
DELETE
statement.
let delete = qians_xql::delete("book")
.filter(qians_xql::eq("id", 1))
.returning(["id", "title"]);
assert_eq!(
delete.to_string(),
"DELETE FROM book WHERE id = 1 RETURNING id, title",
);
Blanket
There are some blanket implementation for traits that defined
in qians_xql::blanket
to assist query building.
Blanket on Expression
Most of expr’s function defined in qians_xql::ops
have method of blanket
implementation of qians_xql::blanket::ExprExt
.
use qians_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 = qians_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 qians_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 qians_xql::expr::Expr;
use qians_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");
Blanket on Table Expression
join
family functions have some blanket implementations.
use qians_xql::blanket::ExprExt;
use qians_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");
Blanket on SELECT
and VALUES
statement
SELECT
and VALUES
are the only statements that can use UNION
family functions.
use qians_xql::blanket::ResultExt;
let query = qians_xql::select([1, 2]).union(qians_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
qians_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!
}
Execution
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 = qians_xql::select(["id", "title"]).from("book");
let rows = qians_xql::exec::fetch_all(query, &pool).await?;
// sqlx::query_as(..).fetch_all
let query = qians_xql::select(["id", "title"]).from("book");
let rows: Vec<Output> = qians_xql::exec::fetch_all_as(query, &pool).await?;
// sqlx::query_scalar(..).fetch_all
let query = qians_xql::select(["id"]).from("book");
let rows: Vec<i32> = qians_xql::exec::fetch_all_scalar(query, &pool).await?;
// or in blanket form
use qians_xql::blanket::StmtExt;
let rows = qians_xql::select(["id", "title"])
.from("book")
.fetch_all(&pool).await?;
let rows: Vec<Output> = qians_xql::select(["id", "title"])
.from("book")
.fetch_all_as(&pool)
.await?;
let rows: Vec<i32> = qians_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.
Notes on str
and String
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.
Re-exports
pub use stmt::delete;
pub use stmt::delete;
pub use stmt::insert;
pub use stmt::insert;
pub use stmt::select;
pub use stmt::select;
pub use stmt::update;
pub use stmt::update;
pub use stmt::values;
pub use stmt::values;
pub use stmt::except;
pub use stmt::except_all;
pub use stmt::intersect;
pub use stmt::intersect_all;
pub use stmt::union;
pub use stmt::union_all;
pub use func::func;
pub use func::avg;
pub use func::count;
pub use func::max;
pub use func::min;
pub use func::sum;
pub use ops::add;
pub use ops::div;
pub use ops::mul;
pub use ops::rem;
pub use ops::sub;
pub use ops::and;
pub use ops::not;
pub use ops::or;
pub use ops::as_field;
pub use ops::as_table;
pub use ops::asc;
pub use ops::desc;
pub use ops::paren;
pub use ops::binop;
pub use ops::postop;
pub use ops::preop;
pub use ops::eq;
pub use ops::ge;
pub use ops::gt;
pub use ops::le;
pub use ops::lt;
pub use ops::ne;
pub use ops::ilike;
pub use ops::isnull;
pub use ops::like;
pub use ops::cross_join;
pub use ops::join;
pub use ops::natural_join;
pub use ops::full_join;
pub use ops::left_join;
pub use ops::right_join;
pub use ops::natural_full_join;
pub use ops::natural_left_join;
pub use ops::natural_right_join;