Update

use diesel::prelude::*;

// single column
diesel::update(products::table.filter(products::id.eq(1)))
    .set(products::price.eq(11.99))
    .execute(&mut conn)?;

// several columns
diesel::update(products::table.filter(products::id.eq(1)))
    .set((products::name.eq("widget-mk2"), products::price.eq(12.5)))
    .execute(&mut conn)?;

use better_duck_diesel::dsl::*;

diesel::update(products::table.filter(products::id.eq(1)))
    .set(products::name.eq(upper(products::name)))  // UPDATE … SET name = upper(name)
    .execute(&mut conn)?;

#[derive(AsChangeset)]
#[diesel(table_name = products)]
struct ProductPatch<'a> {
    name: Option<&'a str>,   // None -> not touched
    price: Option<f64>,
}

diesel::update(products::table.filter(products::id.eq(1)))
    .set(&ProductPatch { name: None, price: Some(19.99) })  // only price is updated
    .execute(&mut conn)?;

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)?;