Can you give examples of special functions or extensions of SQL that you use in your practice?

In practice, working with SQL often involves extensions and special functions that facilitate and speed up data handling. Here are some examples:

• Window Functions — allow calculations over a set of table rows related to the current row, such as ROW_NUMBER(), RANK(), LEAD(), LAG().

• CTE (Common Table Expressions) — temporary named result sets that can be used to simplify complex queries using the WITH clause.

• Filtered aggregate functions — for example, COUNT(*) FILTER (WHERE condition) in PostgreSQL.

• JSON functions — for working with JSON data, such as JSON_EXTRACT(), JSON_ARRAYAGG().

• Date and time functions — for example, DATE_TRUNC(), DATEDIFF().

Example of using a window function:

SELECT employee_id, salary, 
       RANK() OVER (ORDER BY salary DESC) as salary_rank
FROM employees;

This allows ranking employees by salary without grouping data.