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