RETURNING

DuckDB supports RETURNING on INSERT, UPDATE, and DELETE, and the Diesel backend exposes it through .returning(...). It is the way to read server-defaulted or server-computed values back from a write in a single round-trip — no follow-up SELECT.

How it works

Chain .returning(expr) on an insert/update/delete, then execute with a result-returning method instead of .execute:

Rows expected	Method	Returns
exactly one	`.get_result(&mut conn)`	`T` (`Err(NotFound)` if none)
many	`.get_results(&mut conn)`	`Vec<T>`
zero or one	`.get_result(...).optional()`	`Option<T>`

The .returning argument is a single column or a tuple of columns, mirroring .select — the Rust type you load into follows from it.

INSERT

use diesel::prelude::*;

let id: i32 = diesel::insert_into(products::table)
    .values((products::id.eq(4), products::name.eq("doohickey"), products::price.eq(1.0)))
    .returning(products::id)
    .get_result(&mut conn)?;

let returned: Vec<(i32, String)> = diesel::insert_into(products::table)
    .values(&rows)
    .returning((products::id, products::name))
    .get_results(&mut conn)?;

UPDATE

let new_price: f64 = diesel::update(products::table.filter(products::id.eq(1)))
    .set(products::price.eq(11.99))
    .returning(products::price)
    .get_result(&mut conn)?;

DELETE

let removed: Vec<(i32, String)> = diesel::delete(products::table.filter(products::price.lt(1.0)))
    .returning((products::id, products::name))
    .get_results(&mut conn)?;

RETURNING * maps naturally to a #[derive(Queryable, Selectable)] struct: use .returning(Product::as_returning()) to pull a whole row back into a typed struct.

.returning(...) projects columns through the typed loader, so it reads standard types and the narrow unsigned-integer Duck* widths. The composite/semantic Duck* types (and HUGEINT/UHUGEINT) cannot be read this way — use diesel::sql_query("… RETURNING …") with a QueryableByName struct instead. See Type mapping.

Insert

Where RETURNING is most used.

Upsert

RETURNING works after ON CONFLICT too.

Update

Return changed values.

Delete

Return removed values.

Getting Started

CRUD

DuckDB SQL DSL

Types & Pooling

How it works

INSERT

UPDATE

DELETE

See also

Insert

Upsert

Update

Delete

​How it works

​INSERT

​UPDATE

​DELETE

​See also

Insert

Upsert

Update

Delete

How it works

INSERT

UPDATE

DELETE

See also