Trait diesel::expression::SelectableExpression [−] [src]

pub trait SelectableExpression<QS>: Expression {
    type SqlTypeForSelect;
}

Indicates that an expression can be selected from a source. The associated type is usually the same as Expression::SqlType, but is used to indicate that a column is always nullable when it appears on the right side of a left outer join, even if it wasn't nullable to begin with.

Columns will implement this for their table. Certain special types, like CountStar and Bound will implement this for all sources. All other expressions will inherit this from their children.

Associated Types

Implementors