An exclusion constraint is a type of constraint that allows you to specify a set of conditions that, if satisfied by any two rows in a table, will cause an error to be raised when trying to insert or update the table. Exclusion constraints are useful for preventing conflicts or overlaps between rows in a…

In PostgreSQL, a foreign key constraint is a type of constraint that is used to establish a relationship between two tables. The foreign key constraint ensures that the values in a column in one table correspond to the values in a column in another table. To create a foreign key constraint, you first need to…

In PostgreSQL, a primary key constraint is a way to enforce the uniqueness of a column or a group of columns in a table. A primary key constraint is created using the PRIMARY KEY keyword after the column or group of columns that you want to use as the primary key. For example, to create…

In PostgreSQL, the NOT NULL constraint is used to ensure that a column in a table does not contain any NULL values. If you attempt to insert a NULL value into a column with the NOT NULL constraint, PostgreSQL will raise an error and prevent the insertion. To apply the NOT NULL constraint to a…

A check constraint is a type of constraint that allows you to define a condition that must be true for every row in a table. The check constraint can be used to enforce rules on columns, such as limiting the values that can be entered in a particular column or ensuring that certain columns are…

PostgreSQL supports unique constraints to ensure that the values in a particular column ( or set of columns ) are unique across all rows in a table. Unique constraint can be defined on one or more columns of a table. To create a unique constraint in PostgreSQL, you can use the UNIQUE keyword followed by…