Key Joins (SQL Proposal)
The article discusses a new SQL proposal for implementing key joins with compile-time verification. It outlines the syntax, verification rules, and how these joins interact with database schema constraints. The proposal aims to enhance the reliability and soundness of SQL queries involving key joins.
- ▪The Specification introduces an SQL operator for key joins with compile-time verification.
- ▪It includes rules for syntax, verification, and propagation through derived tables.
- ▪The proposal emphasizes the importance of schema-level declarations like PRIMARY KEY and FOREIGN KEY.
Opening excerpt (first ~120 words) tap to expand
7 Specification The Specification realises the Definition as an SQL operator with compile-time verification. It comprises: Syntax (Section 7.2): a syntax for declaring a key join, naming the referencing and referenced sides and their column lists. Compile-time verification (Section 7.3): verification rules that accept a key join only when the DBMS can prove the three conditions of the Definition against the join's intermediate result. One sub-subsection addresses each condition; a fourth covers cases where no proof can be formed. Propagation through derived tables (Section 7.4): rules that carry the proof obligations through views, common table expressions (CTEs), and subqueries.
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