# PostgreSQL Group Functions

#### Chapter 12

5 Steps - 3 Clicks

# PostgreSQL Group Functions

### Introduction

PostgreSQL Group Functions is a type of command which accepts ‘n’ number 0f values as input and return a single value.

PostgreSQL Group Functions can be of different types:

### Description

sum() function is used to calculate the set of values or an expression. For example,the sum function is used to add all the columns details like salaries of employees.

### Syntax

Select Sum<column_name> from <table_name>;

Table_name => Any accurate table.

Column_name =>The operation that one can perform on a column in the table.

### Examples

Below is the example to understand the concept of sum function in the table.

```SQLDB=# select * from employee22;

emp_id | ename | sal   | deptno
---------+-------+-------+--------
1001  | mike  | 14000 |   10
1002  | rambo | 25000 |   20
1003  | kate  | 15500 |   10
1004  | jeo   | 17000 |   20
1005  | finn  | 27000 |   30

(5 rows)

SQLDB=# select sum(sal) from employee22;

sum(sal)
----------
98500

(1 row)```

The above example tells that,when sum() functional operation is performed on a column name like salary, then it will add all the employee salaries and gives the output.

### Description

Average function in PostgreSQL Group Functions is used to calculate the average of a given arrangement of values or an expression. For example the average function is utilized to compute the average of a column name salary in the table.

### Syntax

Select avg(column_name) from <table_name>;

Table_name => Any accurate table.

Column_name =>The operation that one can perform on a column in the table.

### Examples

Below is the example to understand the concept of average function in the table.

```SQLDB=# select * from employee22;

emp_id | ename | sal   | deptno
---------+-------+-------+--------
1001 | mike  | 14000 |  10
1002 | rambo | 25000 |  20
1003 | kate  | 15500 |  10
1004 | jeo   | 17000 |  20
1005 | finn  | 27000 |  30

(5 rows)
SQLDB=# select avg(sal) from employee22;

avg(sal)
------------
27005

(1 row)```

The above example tells that,when avg() functional operation is performed on a column name like salary,then it will average all the employee salaries and gives the output.

### Description

Maximum function is utilized to ascertain the most extreme value of a given arrangement of values or an expression. For illustration the maximum function is utilized to locate the maximum of a column name salary in the table.

### Syntax

Select maximum<column_name>from <table_name>;

Table_name => Any accurate table.

Column_name =>The operation that one can perform on a column in the table.

### Examples

Below is the example to understand the concept of maximum function in the table.

```SQLDB=# select * from employee22;

emp_id | ename | sal   | deptno
----------+-------+-------+--------
1001 | mike  | 14000 |   10
1002 | rambo | 25000 |   20
1003 | kate  | 15500 |   10
1004 | jeo   | 17000 |   20
1005 | finn  | 27500 |   30

(5 rows)

SQLDB=# select max(sal) from employee22;

max(sal)
----------
27500

(1 row)```

The above example tells that,when max() functional operation is performed on a column name like salary, then it will display the highest salary of employee.

### Description

Minimum function is utilized to compute the base estimation of a given arrangement of values or an expression. For illustration the minimum function is utilized to locate the minimum of a column name salary in the table.

### Syntax

Select minimum<column_name>from <table_name>;

Table_name => Any accurate table.

Column_name => The operation that one can perform on a column in the table.

### Examples

Below is the example to understand the concept of minimum function in the table.

```SQLDB=# select * from employee22;

emp_id | ename | sal   | deptno
---------+-------+-------+--------
1001  | mike  | 14000 |   10
1002  | rambo | 25000 |   20
1003  | kate  | 15500 |   10
1004  | jeo   | 17000 |   20
1005  | finn  | 27000 |   30

(5 rows)

SQLDB=# select min(sal) from employee22;

min(sal)
---------
14000

(1 row)```

The above example tells that, when min() functional operation is performed on a column name like salary, then it will display the lowest salary of employee.

### Description

Count function is utilized to compute the aggregate estimation of a given set of values or an expression. For illustration the count function is utilized to locate the aggregate number of employees in the table.

### Syntax

select count<column_name> from <table_name>;

Table_name => Any accurate table.

Column_name => The operation that one can perform on a column in the table.

### Examples

Below is the example to understand the concept of count function in the table.

```SQLDB=# select * from employee22;

emp_id | ename | sal   | deptno
---------+-------+-------+--------
1001 | mike  | 14000 |   10
1002 | rambo | 25000 |   20
1003 | kate  | 15500 |   10
1004 | jeo   | 17000 |   20
1005 | finn  | 27000 |   30

(5 rows)

SQLDB=# select count(emp_id) from employee22;

count(emp_id)
---------------
5
---------------
(1 row)```

The above example tells that, when count() functional operation is performed on a column name like emp_id, then it will count all the employees in the table and display the output as 5.

### Key Points

• PostgreSQL Group Functions – Group function is used to accept ‘n’ number of values and return a single value.
• Sum functions – Adds,average calculates the average of set of values.
• Maximum and minimum functions – Calculates the maximum and minimum values in given set of values.
• Count – Gives total values.