Aggregate Functions
MIN | Returns the smallest value in a given column |
MAX | Returns the largest value in a given column |
SUM | Returns the sum of the numeric values in a given column |
AVG | Returns the average value of a given column |
COUNT | Returns the total number of values in a given column |
COUNT(*) | Returns the number of rows in a table |
In database management system an aggregate function is a function where the values of multiple rows are grouped together as input and on certain criteria to form a single value. Aggregate functions are used to compute against a numeric column data from SELECT statement. This mostly summarize the results of a particular column of selected data.
For example:
SELECT AVG (MARKS) FROM STUDENTS;
This statement will return a single result which contains the average value of everything returned in the Marks column from the Students table.
Another example:
SELECT AVG (SALARY) FROM EMPLOYEE WHERE TITLE=’AVP’;
This statement will return the average salary for all employee whose title is equal to AVP.
Example:
SELECT COUNT (*) FROM STUDENTS;
This statement returns the total number of students. However you can also add additional column or distinct values counts.
Example:-
SELECT COUNT (DISTINCT TITLE) FROM EMPLOYEE;
