Common Table Expressions (EN)

Definition

Common Table Expressions (CTEs) are temporary, named result sets that improve the readability and modularity of complex SQL queries. They are defined with the WITH clause and exist only for the duration of the query. CTEs allow complex queries to be broken down into logical, understandable parts and can contribute to performance optimization through intermediate results.

Architecture

flowchart TD     A[WITH-Klausel] --> B[CTE 1]     A --> C[CTE 2]     A --> D[CTE n]     B --> E[SELECT-Anweisung]     C --> E     D --> E     E --> F[Ergebnis] 

Im Kontext

• Wird typischerweise zusammen mit Fensterfunktionen und rekursiven Abfragen verwendet
• Verwandt zu: Subqueries, Views, Temp Tables
• Beispiel-Einsatz: Hierarchische Abfragen in Organisationstabellen