SQL Aggregate Functions Presentation

Introduction

• The presentation focuses on aggregate functions in SQL.
• Aggregate functions perform calculations on multiple values, returning a single output.

Importance of Aggregate Functions

• Calculating single values from multiple inputs is essential for various applications, like estimating time on Google Maps or monitoring temperatures in a chemical plant.

Key Points

• Aggregate functions ignore null values, except for the COUNT function.
• These functions can be used effectively with GROUP BY and HAVING clauses.

Types of Aggregate Functions

1. COUNT

• Purpose: Returns the number of rows.
• Usage: Can work on both numeric and non-numeric data types.
• Example:
  • SELECT COUNT(*) FROM student; returns all rows.
  • SELECT COUNT(age) FROM student; returns non-null age entries.
  • SELECT COUNT(DISTINCT age) FROM student; returns unique age values.

2. SUM

• Purpose: Returns the sum of a numeric column.
• Usage: Works only on numeric data types.
• Example:
  • SELECT SUM(salary) FROM student; returns the sum of all salary values.
  • SELECT SUM(DISTINCT age) FROM student; returns the sum of unique age values.

3. AVERAGE

• Purpose: Returns the average value of a column.
• Example:
  • SELECT AVG(age) FROM student; returns the average age.
  • SELECT AVG(DISTINCT age) FROM student; calculates the average of unique ages.

4. MINIMUM

• Purpose: Returns the smallest value in a column.
• Example:
  • SELECT MIN(salary) FROM student; returns the minimum salary.

5. MAXIMUM

• Purpose: Returns the largest value in a column.
• Example:
  • SELECT MAX(salary) FROM student; returns the maximum salary.

Practical Use

• Aggregate functions are useful for databases with large data sets, helping to efficiently find minimum, maximum, sum, average, and count of data entries.

Conclusion

• Aggregate functions like COUNT, SUM, AVERAGE, MINIMUM, and MAXIMUM were covered.
• Next presentation will focus on utilizing these functions with GROUP BY and HAVING clauses.

Acknowledgments

• Thank you for engaging with this presentation.