Trait diesel::expression_methods::PgSortExpressionMethods

pub trait PgSortExpressionMethods: Sized {
    // Provided methods
    fn nulls_first(self) -> NullsFirst<Self> { ... }
    fn nulls_last(self) -> NullsLast<Self> { ... }
}

PostgreSQL expression methods related to sorting.

This trait is only implemented for Asc and Desc. Although .asc is implicit if no order is given, you will need to call .asc() explicitly in order to call these methods.

Provided Methods

fn nulls_first(self) -> NullsFirst<Self>

Specify that nulls should come before other values in this ordering.

Normally, nulls come last when sorting in ascending order and first when sorting in descending order.

Example

diesel::insert_into(nullable_numbers)
    .values(&vec![
        nullable_number.eq(None),
        nullable_number.eq(Some(1)),
        nullable_number.eq(Some(2)),
    ])
    .execute(connection)?;

let asc_default_nulls = nullable_numbers.select(nullable_number)
    .order(nullable_number.asc())
    .load(connection)?;
assert_eq!(vec![Some(1), Some(2), None], asc_default_nulls);

let asc_nulls_first = nullable_numbers.select(nullable_number)
    .order(nullable_number.asc().nulls_first())
    .load(connection)?;
assert_eq!(vec![None, Some(1), Some(2)], asc_nulls_first);

fn nulls_last(self) -> NullsLast<Self>

Specify that nulls should come after other values in this ordering.

Normally, nulls come last when sorting in ascending order and first when sorting in descending order.

Example

diesel::insert_into(nullable_numbers)
    .values(&vec![
        nullable_number.eq(None),
        nullable_number.eq(Some(1)),
        nullable_number.eq(Some(2)),
    ])
    .execute(connection)?;

let desc_default_nulls = nullable_numbers.select(nullable_number)
    .order(nullable_number.desc())
    .load(connection)?;
assert_eq!(vec![None, Some(2), Some(1)], desc_default_nulls);

let desc_nulls_last = nullable_numbers.select(nullable_number)
    .order(nullable_number.desc().nulls_last())
    .load(connection)?;
assert_eq!(vec![Some(2), Some(1), None], desc_nulls_last);

Implementors