Module expression

AST types representing various typed SQL expressions.

Almost all types implement either Expression or AsExpression.

The most common expression to work with is a Column. There are various methods that you can call on these, found in expression_methods.

You can also use numeric operators such as + on expressions of the appropriate type.

Any primitive which implements ToSql will also implement AsExpression, allowing it to be used as an argument to any of the methods described here.

Modules

array_comparisoni-implement-a-third-party-backend-and-opt-into-breaking-changes

This module contains the query dsl node definitions for array comparison operations like IN and NOT IN

existsi-implement-a-third-party-backend-and-opt-into-breaking-changes

This module contains the query dsl node definition for EXISTS expressions

expression_types

Possible types for []Expression::SqlType]

functions

Helper macros to define custom sql functions

is_aggregate

Possible values for ValidGrouping::IsAggregate

Structs

CaseWhen

A SQL CASE WHEN ... END expression

Concati-implement-a-third-party-backend-and-opt-into-breaking-changes

This type represents a string concat operator

SqlLiteral

Returned by the sql() function.

UncheckedBind

Returned by the SqlLiteral::bind() method when binding a value to a fragment of SQL.

Traits

AppearsOnTable

Indicates that all elements of an expression are valid given a from clause.

AsExpression

Converts a type to its representation for use in Diesel’s query builder.

BoxableExpression

Helper trait used when boxing expressions.

Expression

Represents a typed fragment of SQL.

IntoSql

Converts a type to its representation for use in Diesel’s query builder.

MixedAggregates

Can two IsAggregate types appear in the same expression?

NonAggregateNon-unstable

Trait alias to represent an expression that isn’t aggregate by default.

QueryMetadata

A helper to translate type level sql type information into runtime type information for specific queries

Selectable

Trait indicating that a record can be selected and queried from the database.

SelectableExpression

Indicates that an expression can be selected from a source.

SelectableHelper

This helper trait provides several methods for constructing a select or returning clause based on a Selectable implementation.

TypedExpressionType

Marker trait for possible types of Expression::SqlType

ValidGrouping

Is this expression valid for a given group by clause?

Derive Macros

AsExpression

Implements all required variants of AsExpression

Selectable

Implements Selectable

ValidGrouping

Implements ValidGrouping