PostgreSQL constraints keep invalid data out of your tables. This guide explains NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK and DEFAULT with runnable PostgreSQL examples, plus ways to inspect and remove constraints. What are constraints in PostgreSQL? A constraint is a rule that PostgreSQL checks when data is inserted or changed. Violations usually cause the statement to fail rather than silently storing inconsistent data. Constraints are useful alongside application… Read More »PostgreSQL Constraints Explained: PRIMARY KEY, FOREIGN KEY and CHECK