SQL COUNT SUM AVG - Learn2Done

Count() Function: It returns the number of rows in selected column.

Syntax:

SELECT COUNT(column_name) FROM table_name
WHERE condition;

SAMPLE STUDENTS DATABASE:

Data

Example: To count the number of rows of Roll_No in students table.

SELECT COUNT(Roll_No) FROM students;

This will result as:

Data

COUNT(Roll_No)

SUM() Function: It returns the total sum of selected numeric column.

Syntax:

SELECT SUM(column_name) FROM table_name
WHERE condition;

Example: To sum the marks all students in students table.

SELECT SUM(Marks) FROM students;

This will result as:

Data

SUM(Marks)

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AVG() Function: It returns the average of selected numeric column.

Syntax:

SELECT AVG(column_name) FROM table_name
WHERE condition;

Example: To find the average of marks all students in students table.

SELECT AVG(Marks) FROM students;

This will result as:

Data

AVG(Marks)