SQL Functions Mastery: String, Date, Math & Aggregate Tutorial

SQL Tutorial #28 - String Functions in SQL Explained with Examples

Creating And Using Functions in MS SQL - With Examples!!

Functions In SQL Explained In Detail | SQL Functions With Examples | SQL For Beginners | SimpliCode

SQL Aggregate Functions - SUM(), AVG(), MIN(), MAX() and GROUP BY

Basic Aggregate Functions in SQL (COUNT, SUM, AVG, MAX, and MIN)