Aggregate Function

SQL aggregate functions are used to perform calculations on a set of values and return a single summarised result. Aggregate functions operate on multiple rows but return a single value per group or entire table.

SQL COUNT() Function

The COUNT() function provides the number of rows that match a specified condition. It is often used to determine:

Total records in a table
Records that meet a specific filter

Example: First, we will create a demo SQL database and table, on which we will use the COUNT() Function command.

SELECT COUNT(Name)
FROM GeeksTab;

Output:

SQL AVG() Function

The AVG() function provides the average value of a numeric column, helping you determine central tendencies in your data. This is useful for understanding the mean value of a set of numbers, such as salaries, prices, or scores.

Now let's understand this with the help of query:

SELECT AVG(Salary)
FROM GeeksTab;

Output:

SQL SUM() Function

The SUM() function calculates the total sum of a numeric column. It is ideal for calculating:

Total sales
Total revenue
Any cumulative numeric value

Now let's understand this with the help of query:

SELECT SUM(Salary)
FROM GeeksTab;

Output:

Note: COUNT(), AVG() and SUM() primarily used for numerical analysis and aggregation.

SQL MIN() Function

The MIN() function returns the smallest value in a specified column.

Works with numeric, string, and date data types.
Can be used with DISTINCT to find the smallest among unique values.
Useful for identifying minimum prices, earliest dates, youngest age, etc.

SELECT MIN(Salary) AS Min_Salary
FROM GeeksTab;

Output:

SQL MAX() Functions

The MAX() function returns the largest value in a specified column.

Works with numeric, string, and date data types.
Can be combined with GROUP BY, HAVING, and subqueries for advanced analysis.
Useful for identifying highest salaries, latest dates, oldest age, etc.

Now let's understand this with the help of query:

SELECT MAX(Salary) AS Max_Salary
FROM GeeksTab;

Output:

Using MIN() and MAX() with HAVING Clause

Suppose we want to fetch a person's name with max age as column max_age then we can use the following query but with some conditions like min age at least 22

SELECT Name, MAX(Salary) AS max_salary
FROM GeeksTab
GROUP BY Name
HAVING MIN(Salary) > 5000;

Output:

Note:
Aggregate functions ignore NULL values by default, unless explicitly handled.
MIN() and MAX() used to find extremes or boundary values in a dataset.

SQL COUNT() Function

SQL AVG() Function

SQL SUM() Function

SQL MIN() Function

SQL MAX() Functions

Using MIN() and MAX() with HAVING Clause

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