• EN
    Blog

    Cybertec Logo

    • Services
      • Requirement Analysis
      • PostgreSQL consulting
      • PostgreSQL migration
        • Migration from Oracle
        • Migrating from MySQL / MariaDB
        • CYBERTEC Migrator
      • PostgreSQL Infrastructure
        • Setup & Installation
        • Kubernetes
        • Database architecture
      • PostgreSQL development
        • Database modeling
        • Functions & Features
      • Update & Upgrade
      • Optimization & Security
        • PostgreSQL Health Check
        • Performance Tuning
        • Enterprise Security
        • Security Audit
      • Troubleshooting & Data Recovery
      • PostgreSQL clustering and HA
        • Clustering and failover
        • High availability with Patroni
        • Synchronous and asynchronous replication
        • Scaling with PL/Proxy
      • Spatial Services
        • GIS Tooling
        • PostGIS OSM Downloader
      • CYBERTEC Partner Network
    • Support
      • Standard PostgreSQL Support
        • Product Support
        • 9/5 Basic Support
        • 24/7 Basic Support
        • 24/7 Enterprise Support
      • Advanced PostgreSQL Support
        • 9/5 Remote DBA
        • 24/7 Remote DBA
        • 9/5 Dedicated DBA
        • 24/7 Cloud-based Support
      • Support for Reseller
        • 3rd Level Support
        • CYBERTEC Partner Network
    • Products
      • Our Products
        • CYPEX – Build Apps & Forms
        • CYBERTEC PostgreSQL Enterprise Edition
        • CYBERTEC Migrator
        • PostgreSQL Transparent Data Encryption
        • Scalefield – Private Cloud
        • Data Masking for PostgreSQL
        • PL/pgSQL_sec – Fully encrypted stored procedures
      • PostgreSQL Tools & Extensions
        • pg_timetable – Advanced Job Scheduling
        • pg_show_plans – Monitoring Execution Plans
        • pgwatch – PostgreSQL Monitoring Tool
        • pg_squeeze – Shrinks Tables
        • Walbouncer – Enterprise Grade Partial Replication
        • PGConfigurator – Visual PostgreSQL Configuration
        • Patroni Environment Setup
      • Assessment Packages
        • Data Science Assessment Package
        • Start-Up Assessment Package
        • Spatial Data Assessment Package
      • CYBERTEC Partner Network
    • Training
    • PostgreSQL
      • Advantages of PostgreSQL
      • PostgreSQL Books
      • Solutions – Who uses PostgreSQL
        • PostgreSQL for Startups
        • PostgreSQL for governments and public services
        • Longlife solutions
      • Business Cases
        • Fraud Detection
        • PostgreSQL for biotech and scientific applications
    • Data Science
      • Data Science Overview
      • Machine Learning
      • Big Data Analytics
    • Contact
      • Jobs
      • Contact

    Posts

    Tag: constraint

    24.01.2023 | Laurenz Albe

    A unique constraint where NULL conflicts with everything

    © Laurenz Albe 2022 I have been faced with a request for an unusual unique constraint that puzzled me for a while. Since the solution I came up with is a nice show-case for range data types, I’ll share it with you. Also, it allows me to rant some about NULL, which is a temptation […]

    Read more
    30.11.2021 | Hans-Jürgen Schönig

    Primary Keys vs. UNIQUE Constraints in PostgreSQL

    Most of my readers will know about primary keys and all kinds of table constraints. However, only a few of you may have ever thought about the difference between a primary key and a UNIQUE constraint. Isn’t it all just the same? In both cases, PostgreSQL will create an index that avoids duplicate entries. So […]

    Read more
    24.06.2021 | Hans-Jürgen Schönig

    PostgreSQL: Constraints over multiple rows

    In PostgreSQL and many other relational databases, constraints are an integral part of the feature set. Many people are aware of primary keys, foreign keys, CHECK-constraints, table constraints and so on. However, from time to time, the situation is way more complicated. That’s when some more advanced techniques are needed to enforce integrity in the […]

    Read more
    27.10.2020 | Hans-Jürgen Schönig

    PostgreSQL: Foreign keys and insertion order in SQL

    In SQL, the concept of foreign keys is an important one that can be found in all professional databases used in the industry. The core idea is to prevent your PostgreSQL database from storing inconsistent data by enforcing constraints ensuring the correctness of your tables (at least as far as relations between objects are concerned). […]

    Read more
    25.04.2019 | Laurenz Albe

    Triggers to enforce constraints

      Sometimes you want to enforce a condition on a table that cannot be implemented by a constraint. In such a case it is tempting to use triggers instead. This article describes how to do this and what to watch out for. It will also familiarize you with the little-known PostgreSQL feature of “constraint triggers”. […]

    Read more

    logo

    CYBERTEC PostgreSQL International GmbH
    Römerstraße 19
    2752 Wöllersdorf
    AUSTRIA

    +43 (0) 2622 93022-0
    office@cybertec.at
    twitter.com/PostgresSupport
    github.com/cybertec-postgresql

    Our Services

    • Administration
    • Replication
    • Consulting
    • Database Design
    • Support
    • Migration
    • Development

     

    SUPPORT CUSTOMERS
    Go to the support platform >>

    Newsletter

    Check out previous newsletters!

    Stay well informed about PostgreSQL by subscribing to our newsletter.

    © 2000–2023 CYBERTEC PostgreSQL International GmbH
    • IMPORTANT INFORMATION ABOUT COVID-19
    • Contact
    • Data protection policy
    • Imprint
    • Terms and Conditions