Struct Optional 

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

This is the argument type used by the optional combinator.

Joining more optional columns can be done with the Optional::and method. Finally it is possible to return expressions or selections using Optional::then and Optional::then_select.

Implementations

impl<'outer, 'inner, S> Optional<'outer, 'inner, S>

pub fn and<T: MyTyp>( &mut self, col: impl IntoExpr<'inner, S, Typ = Option<T>>, ) -> Expr<'inner, S, T>

Join an optional column to the current row.

If the joined column is None, then the whole optional combinator will return None.

pub fn is_none(&self) -> Expr<'outer, S, bool>

Return a bool column indicating whether the current row does not exists.

pub fn is_some(&self) -> Expr<'outer, S, bool>

Return a bool column indicating whether the current row exists.

pub fn and_then<T: MyTyp<Sql: Nullable>>( &self, col: impl IntoExpr<'inner, S, Typ = Option<T>>, ) -> Expr<'outer, S, Option<T>>

This is much like combining Self::and with Self::then, but it allows returning an optional value without mutating self.

pub fn then<T: MyTyp<Sql: Nullable> + 'outer>( &self, col: impl IntoExpr<'inner, S, Typ = T>, ) -> Expr<'outer, S, Option<T>>

Return Some column if the current row exists and None column otherwise.

pub fn then_select<Out: 'static>( &self, d: impl IntoSelect<'inner, S, Out = Out>, ) -> Select<'outer, S, Option<Out>>

Returns a Select with optional result.