Struct Aggregate

pub struct Aggregate<'outer, 'inner, S> { /* private fields */ }

This is the argument type used for aggregates.

While it is possible to join many tables in an aggregate, there can be only one result. (The result can be a tuple or struct with multiple values though).

Implementations

impl<'outer: 'inner, 'inner, S: 'outer> Aggregate<'outer, 'inner, S>

pub fn filter_on<T>( &mut self, val: impl IntoColumn<'inner, S, Typ = T>, on: impl IntoColumn<'outer, S, Typ = T>, )

Filter the rows of this sub-query based on a value from the outer query.

pub fn avg( &'inner self, val: impl IntoColumn<'inner, S, Typ = f64>, ) -> Column<'outer, S, Option<f64>>

Return the average value in a column, this is None if there are zero rows.

pub fn max<T>( &'inner self, val: impl IntoColumn<'inner, S, Typ = T>, ) -> Column<'outer, S, Option<T>>

where T: NumTyp,

Return the maximum value in a column, this is None if there are zero rows.

pub fn sum<T>( &'inner self, val: impl IntoColumn<'inner, S, Typ = T>, ) -> Column<'outer, S, T>

where T: NumTyp,

Return the sum of a column.

pub fn count_distinct<T>( &'inner self, val: impl IntoColumn<'inner, S, Typ = T>, ) -> Column<'outer, S, i64>

where T: EqTyp,

Return the number of distinct values in a column.

pub fn exists(&'inner self) -> Column<'outer, S, bool>

Return whether there are any rows.

Methods from Deref<Target = Rows<'inner, S>>

pub fn join<T: Table<Schema = S>>(&mut self) -> Column<'inner, S, T>

Join a table, this is like a super simple Iterator::flat_map but for queries.

After this operation Rows has rows for the combinations of each original row with each row of the table. (Also called the “Carthesian product”)

For convenience there is also Table::join.

pub fn filter(&mut self, prop: impl IntoColumn<'inner, S, Typ = bool>)

Filter rows based on a column.

pub fn filter_some<Typ>( &mut self, val: impl IntoColumn<'inner, S, Typ = Option<Typ>>, ) -> Column<'inner, S, Typ>

Filter out rows where this column is None.

Returns a new column with the unwrapped type.

Trait Implementations

impl<'outer, 'inner, S> Deref for Aggregate<'outer, 'inner, S>

type Target = Rows<'inner, S>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<'outer, 'inner, S> DerefMut for Aggregate<'outer, 'inner, S>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.