Tag: constraint

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Here you can find all blog posts about the Tag: constraint. You can go back to all blog posts or take a look into our other categories & tags.

Broken foreign keys: how can that happen in PostgreSQL?

by Laurenz Albe | 12.2023
  One of the fundamental requirements for a relational database is that the transaction system always maintains consistency. That means […]

Exclusion constraints in PostgreSQL and a tricky problem

by Christoph Berg | 09.2023
Exclusion constraints are a feature that is not very well known, but can be used to implement highly sophisticated constraints. […]

Breaking your PostgreSQL database with bad CHECK constraints

by Laurenz Albe | 03.2023
  I am on a spree! After writing about breaking your database and transaction ID wraparound, here I am writing […]

A unique constraint where NULL conflicts with everything

by Laurenz Albe | 01.2023
  I have been faced with a request for an unusual unique constraint that puzzled me for a while. Since […]

Primary Keys vs. UNIQUE Constraints in PostgreSQL

by Hans-Jürgen Schönig | 11.2021
Most of my readers will know about primary keys and all kinds of table constraints. However, only a few of […]

Constraints over multiple rows in PostgreSQL

by Hans-Jürgen Schönig | 06.2021
Manage constraints over multiple rows: In PostgreSQL and many other relational databases, constraints are an integral part of the feature […]

PostgreSQL: Foreign keys and insertion order in SQL

by Hans-Jürgen Schönig | 10.2020
In SQL, the concept of foreign keys is an important one that can be found in all professional databases used […]

PostgreSQL: Useful new data types - CREATE DOMAIN

by Hans-Jürgen Schönig | 07.2020
UPDATED 08.05.2023 - SQL and especially PostgreSQL provide a nice set of general purpose data types you can use to […]

Triggers to enforce constraints in PostgreSQL

by Laurenz Albe | 04.2019
  Sometimes you want to enforce a condition on a table that cannot be implemented by a constraint. In such […]

PostgreSQL exclusion constraints: Beyond UNIQUE

by Hans-Jürgen Schönig | 07.2016
UPDATED AUGUST 2023: A couple of years ago, PostgreSQL introduced so called “exclusion constraints”, which are defined with the EXCLUDE […]
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