SQL Series: Part 3— SQL Aggregate Functions with Sample

Check Out Part 2 of the SQL Series:

SQL Series Part 2 — SQL Joins (INNER / LEFT / RIGHT / FULL OUTER / SELF / CROSS)

Credit: Google Image

What is Aggregate Function?

Definition: A set of functions used to perform calculations or summarize data across multiple rows in a table, and return a single value.

Common SQL Aggregations:

• COUNT: Counts the number of rows in a specified table or view
• SUM: Calculates the sum of all values in a specified column
• AVG: Calculates the average value of a specified column
• MAX: Returns the maximum value in a specified column
• MIN: Returns the minimum value in a specified column

To better understand and visualize how the aggregate functions works in the real world, the following employee table is created for illustration:

Employee Table
+-------------+-------------------+--------+
| employee_id |       title       | salary |
+-------------+-------------------+--------+
|        1001 | manager           | 100000 |
|        1002 | data…