Trait diesel::prelude::QuerySource

pub trait QuerySource {
    type FromClause;
    type DefaultSelection: SelectableExpression<Self>;

    // Required methods
    fn from_clause(&self) -> Self::FromClause;
    fn default_selection(&self) -> Self::DefaultSelection;
}

Represents a type which can appear in the FROM clause. Apps should not need to concern themselves with this trait.

Types which implement this trait include:

• Tables generated by the table! macro
• Internal structs which represent joins
• A select statement which has had no query builder methods called on it, other than those which can affect the from clause.

Required Associated Types

type FromClause

The type returned by from_clause

type DefaultSelection: SelectableExpression<Self>

The type returned by default_selection

Required Methods

fn from_clause(&self) -> Self::FromClause

The actual FROM clause of this type. This is typically only called in QueryFragment implementations.

fn default_selection(&self) -> Self::DefaultSelection

The default select clause of this type, which should be used if no select clause was explicitly specified. This should always be a tuple of all the desired columns, not star

Implementors

impl<From> QuerySource for SelectStatement<From>where From: AsQuerySource, <From::QuerySource as QuerySource>::DefaultSelection: SelectableExpression<Self>,

type FromClause = <<From as AsQuerySource>::QuerySource as QuerySource>::FromClause

type DefaultSelection = <<From as AsQuerySource>::QuerySource as QuerySource>::DefaultSelection

impl<S> QuerySource for Only<S>where S: Table + Clone, <S as QuerySource>::DefaultSelection: ValidGrouping<()> + SelectableExpression<Only<S>>,

Available on crate feature postgres_backend only.

type FromClause = Only<S>

type DefaultSelection = <S as QuerySource>::DefaultSelection

impl<S> QuerySource for Alias<S>where Self: Clone, S: AliasSource, S::Target: QuerySource, <S::Target as QuerySource>::DefaultSelection: FieldAliasMapper<S>, <<S::Target as QuerySource>::DefaultSelection as FieldAliasMapper<S>>::Out: SelectableExpression<Self>,

type FromClause = Alias<S>

type DefaultSelection = <<<S as AliasSource>::Target as QuerySource>::DefaultSelection as FieldAliasMapper<S>>::Out