PostgreSQL as the SQL Standard-compliant RDBMS

When selecting a Relational Database Management System (RDBMS), one of the critical considerations is compliance with the SQL standard. Among the widely-used RDBMS options, PostgreSQL stands out for its strict adherence to the SQL standard. This article explores why PostgreSQL is often considered the closest to the SQL standard and discusses how it compares to other popular RDBMS systems like Oracle Database, Microsoft SQL Server, and MySQL.

SQL Compliance in PostgreSQL

PostgreSQL is renowned for its compliance with the SQL standard, particularly with SQL:2016. This compliance is reflected in its robust implementation of advanced features such as window functions, Common Table Expressions (CTEs), and full outer joins. These features not only align with the standard but also offer a high level of flexibility and expressiveness, allowing for more complex and efficient queries.

Extensibility and Flexibility

Another key factor that sets PostgreSQL apart is its extensibility. The system allows users to define their own data types, operators, and functions. This capability enhances its compliance with SQL standards and provides unprecedented flexibility in handling complex queries. By extending its capabilities, PostgreSQL can adapt to a wide range of use cases, from simple to highly specialized applications.

Rich Feature Set

PostgreSQL's feature set is extensive and includes advanced data types such as JSON, XML, arrays, and full-text search. It also supports various indexing methods, all while maintaining standard SQL syntax. This rich feature set enables developers to leverage both standard and advanced SQL capabilities to build robust and scalable applications. The ability to support diverse data types and advanced querying techniques makes PostgreSQL a versatile choice for a wide range of database management needs.

Community and Documentation

A strong and supportive community is a crucial aspect of any RDBMS. PostgreSQL has a thriving community with comprehensive documentation that often references SQL standards. This makes it easier for developers to understand and implement standard-compliant SQL, enhancing the overall reliability and maintainability of applications built on PostgreSQL. The combination of extensive documentation and a robust community ensures that developers can find help, resources, and best practices to implement their SQL standards effectively.

Comparison with Other RDBMSs

While other popular RDBMSs such as Oracle Database, Microsoft SQL Server, and MySQL also support SQL standards, they may deviate with proprietary extensions or variations. For instance, Oracle has its own set of proprietary features and syntax that may not be fully compatible with the SQL standard. Similarly, MySQL, while open-source and standards-compliant, has some proprietary extensions and may not fully adhere to certain standard features.

Other Standards and Features

Mimer SQL claims 100% compliance with the core ISO 2016 standard, and it has many non-core features. However, when it comes to more specialized or optional features, no current RDBMS fully implements most of the SQL standard. For example, there are entire sections in the standard on Temporal and Bi-Temporal data standards, which are not fully supported by most RDBMS systems. As of now, only DB2 has made an attempt to support these features, but it only covers single Temporal data and not Bi-Temporal data. Similarly, there is a developing standard for handling JSON documents in RDBMS, and DB2, Oracle, PostgreSQL, Microsoft SQL Server, and Informix all have varying levels of support for JSON data, none of which are close to the developing standard.

Conclusion

While the SQL standard is broad and covers many specialty and optional features, PostgreSQL remains one of the most standard-compliant RDBMS options. Its adherence to SQL:2016, extensive feature set, flexibility, and strong community make it a preferred choice for developers seeking a reliable, standards-compliant RDBMS. When evaluating different RDBMS systems, it is essential to consider factors like SQL compliance, extensibility, and feature richness to ensure that the chosen system meets the specific needs of your project.

Keywords: PostgreSQL, SQL Standard, RDBMS