SQL Functions
Like as any
other programming language, SQL also supports a rich set of inbuild functions.
These functions greatly increase the ability to manipulate the information
stored in a database. These functions are also referred as Oracle Functions.
SQL Functions 
SQL
functions accept arguments as an input and returns result as an output
Arguments can be some constant values, or expressions, or column names related
to tables. The general format of the SQL function is as given below:
Function_name(argument1,
argument2,…,argument)
SQL
functions can be categorized into two parts, based on whether they operate on a
single row or a set or rows.
Aggregate functions (Group function)

Functions
that operate on a set or rows are called Aggregate or Group function.

These
functions accept a set or rows, i.e. a group, as an input. They return only a
single row as an output. So, if five rows are given as an input, there will be
only single result as an output.

For
example, MAX is an aggregate function. It finds maximum number out of set of
numbers, and returns single value as an answer.
6 List Types of Aggregate functions
1. MAX
2. MIN
3. SUM
4. AVG
5. COUNT(*)
6. COUNT
EID

ENAME

BIRTHDATE

SALARY

CITY

E01

Tulsi

26JAN2001

13000

Anand

E02

Gopi

10Feb2004

16000

Vvnagar

E03

Rajshree

31Jul2006

17000

Anand

E04

Vaishali

12MAR2008

13000

Mehsana

E05

Laxmi

12MAR2008

25000


E06

Shivali

01SEP2010

20000

Surat

1. MAX
MAX (ColumnName)
Returns maximum value for
a given column.
EX: Find maximum salary from Employee table.
SELECT MAX (salary) “Max Salary” FROM
Employee;
Output: Max Salary
25000
database administrators
2. MIN
MIN (ColumnName)
Returns minimum value for
a given column.
EX: Find minimum salary
from Employee table.
SELECT MIN (Salary) “Min Salary” FROM
Employee;
Output: Min Salary
13000
3. SUM
SUM ([ Distinct  All ]
columnName)
Returns sum of all vales
for a given column
If ‘distinct’ is
provided, duplicate values will be considered only once. By default, ‘All’ is
considered. This is illustrated in following example.
EX: Find sum of all and
distinct salaries from Employee table.
SELECT SUM (salary), SUM (Distinct salary) FROM Employee;
Output: SUM (SALARY) SUM (DISTINCTSALARY)
104000 79000
4. AVG
AVG ([ Distinct All ]
columnName)
Returns average of all values
for a given column.
If ‘distinct’ is
provided, duplicate values will be considered only once. By default, ‘All’ is
considered. This is illustrated in following table.
EX: Find average of all
salaries from Employee table.
SELECT AVG (Salary), AVG (Distinct salary) FROM Employee;
Output: AVG(SALARY) AVG(DISTiNCTSALARY)
17.333.333 15800
5. COUNT(*)
COUNT ( * )
Returns number of rows in
a table including duplicates and having null values.
EX: Find total number of
employees.
SELECT COUNT (*) FROM Employee;
Output: COUNT(*)
6
6. COUNT
COUNT ([ Distinct  All ]
columnName )
Returns number of rows
where column does not contain null value.
EX: The following
example clarifies differences between count and count (*)
SELECT COUNT (*) “C*”, COUNT(city) “CC”,
COUNT (Distinct city) “CDC” FROM Employee;
Output: C* CC CDC
6 5 4
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