What are Aggregate Functions in SQL? Easy Guide for Beginners

Aggregate = “Total / Summary”.

In SQL, aggregate functions are used to calculate values from multiple rows together (instead of checking each row one by one).

Example: In a class of students, instead of checking every student’s marks separately, we calculate total marks, average marks, highest marks, etc.

Common Aggregate Functions:

1. SUM() → Adds values
   • Example: SUM(salary) = total salary of all employees.
   • Like: Total bill amount in a restaurant .
2. AVG() → Average value
   • Example: AVG(marks) = average marks of students.
   • Like: Average run rate in cricket .
3. COUNT() → Number of rows
   • Example: COUNT(student_id) = total students in class.
   • Like: Counting how many players are on the field.
4. MAX() → Highest value
   • Example: MAX(salary) = highest salary in company.
   • Like: Highest score in cricket match.
5. MIN() → Lowest value
   • Example: MIN(marks) = lowest marks in exam.
   • Like: Minimum bus ticket price.

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Real-Life Analogy (Cricket Example):

Imagine we have a scoreboard of players’ runs:

Player	Runs
Virat	80
Rohit	50
Dhoni	40
Hardik	30

• SUM(runs) → 200 (total team score)
• AVG(runs) → 50 (average runs)
• COUNT(runs) → 4 (number of players)
• MAX(runs) → 80 (highest score)
• MIN(runs) → 30 (lowest score)

Quick Recap for Freshers:

• Aggregate = Summary function.
• Works on group of rows, not single row.
• Used with GROUP BY often (like marks per subject, sales per city).