Trait diesel::expression::NonAggregate
source · [−]pub trait NonAggregate: ValidGrouping<()> { }Expand description
Trait alias to represent an expression that isn’t aggregate by default.
This trait should never be implemented directly. It is replaced with a
trait alias when the unstable feature is enabled.
This alias represents a type which is not aggregate if there is no group by
clause. More specifically, it represents for types which implement
ValidGrouping<()> where IsAggregate is is_aggregate::No or
is_aggregate::Yes.
While this trait is a useful stand-in for common cases, T: NonAggregate
cannot always be used when T: ValidGrouping<(), IsAggregate = No> or
T: ValidGrouping<(), IsAggregate = Never> could be. For that reason,
unless you need to abstract over both columns and literals, you should
prefer to use ValidGrouping<()> in your bounds instead.