Aggregate function

Database Management
System
Rayhan Chowdhury
22nd Batch , Exam Roll-796
Department of Computer Science and Engineering
22 September ,
2018

Aggregate function
Aggregate functions are functions that take a collection of values as input and return a single value.
► Behavior of Aggregate Functions:
*Operates - on a single column
*Return - a single value.
*Ignore NULL Values
The ISO standard defines five (5) Aggregate Functions

5 built in aggregate functions in SQL
Count01
02
04
03
05
SUM
AVG
MAX
MIN

AVG
It returns the average of a data value
Syntax :
SELECT AVG [column-name] FROM [Table-name]

E_ID E_Name Age City Salary
E_001 Rakib 24 Dhaka 20,000
E_002 Rafi 21 Savar 18,000
E_003 Razu 30 khulna 35,000
E_004 Rayhan 21 Savar 22,000
E_005 Rahul 19 Sylhet 26,000
Table Name- Employee
Input :
SELECT AVG (Salary) FROM Employee
Example :
Output :
AVG (Salary) = 24,200

SUM
It returns the addition of a data value
Syntax :
SELECT SUM [column-name] FROM [Table-name]

E_002 Rafi 21 Savar 18,000
Input :
SELECT SUM (Salary) FROM Employee
Example :
Output :
SUM (Salary) = 121,000

MAX
It returns the maximum value of a column
Syntax :
SELECT MAX [column-name] FROM [Table-name]

E_002 Rafi 21 Savar 18,000
Input :
SELECT MAX (Age) FROM Employee
Example :
Output :
MAX (Age) = 30

MIN
It returns the minimum value of a column
Syntax :
SELECT MIN [column-name] FROM [Table-name]

E_002 Rafi 21 Savar 18,000
Input :
SELECT MIN (Salary) FROM Employee
Example :
Output :
MIN (Salary) = 18,000

COUNT
It returns total number of values in a given
column
Syntax :
SELECT COUNT [column-name] FROM [Table-name]

E_002 Rafi 21 Savar 18,000
Input :
SELECT COUNT (E_ID) FROM Employee
Example :
Output :
COUNT (E_ID) = 5

Aggregate function

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Aggregate function