Trait AsInExpression

pub trait AsInExpression<T: SqlType + TypedExpressionType> {
    type InExpression: MaybeEmpty + Expression<SqlType = T>;

    // Required method
    fn as_in_expression(self) -> Self::InExpression;
}

Available on crate feature i-implement-a-third-party-backend-and-opt-into-breaking-changes only.

This trait describes how a type is transformed to the IN (values) value expression

Diesel provided several implementations here:

• An implementation for any Iterator over values that implement AsExpression<ST> for the corresponding sql type ST. The corresponding values clause will contain bind statements for each individual value.
• An implementation for select statements, that returns a single field. The corresponding values clause will contain the sub query.

This trait is exposed for custom third party backends so that they can restrict the QueryFragment implementations for In and NotIn.

Required Associated Types

type InExpression: MaybeEmpty + Expression<SqlType = T>

Type of the expression returned by AsInExpression::as_in_expression

Required Methods

fn as_in_expression(self) -> Self::InExpression

Construct the diesel query dsl representation of the IN (values) clause for the given type

Implementors

impl<'a, ST, QS, DB, GB> AsInExpression<ST> for BoxedSelectStatement<'a, ST, QS, DB, GB>

where ST: SqlType + TypedExpressionType, Subselect<BoxedSelectStatement<'a, ST, QS, DB, GB>, ST>: Expression<SqlType = ST>,

type InExpression = Subselect<BoxedSelectStatement<'a, ST, QS, DB, GB>, ST>

impl<I, T, ST> AsInExpression<ST> for I

where I: IntoIterator<Item = T>, T: AsExpression<ST>, ST: SqlType + TypedExpressionType,

type InExpression = Many<ST, T>

impl<ST, F, S, D, W, O, LOf, G, H, LC> AsInExpression<ST> for SelectStatement<F, S, D, W, O, LOf, G, H, LC>

where ST: SqlType + TypedExpressionType, Subselect<Self, ST>: Expression<SqlType = ST>, Self: SelectQuery<SqlType = ST>,

type InExpression = Subselect<SelectStatement<F, S, D, W, O, LOf, G, H, LC>, ST>