PostgreSQL – CONSTRAINTS Constraints are the rules enforced on data columns on table. These are used to prevent invalid data from being entered into the database. This ensures the accuracy and reliability of the data in the database. Constraints could be column level or table level. Column level constraints are applied only to one column […]

PostgreSQL – GROUP BY The PostgreSQL GROUP BY clause is used in collaboration with the SELECT statement to group together those rows in a table that have identical data. This is done to eliminate redundancy in the output and/or compute aggregates that apply to these groups. The GROUP BY clause follows the WHERE clause in […]

PostgreSQL – HAVING Clause The HAVING clause allows us to pick out particular rows where the function”s result meets some condition. The WHERE clause places conditions on the selected columns, whereas the HAVING clause places conditions on groups created by the GROUP BY clause. Syntax The following is the position of the HAVING clause in […]