What are SQL Functions?

SQL provides many built-in functions to perform operations on data. These functions are useful while performing mathematical calculations, string concatenations, sub-strings etc. SQL functions are divided into two categories,

  1. Aggregate Functions
  2. Scalar Functions

Aggregate Functions

These functions return a single value after performing calculations on a group of values. Following are some of the frequently used Aggregrate functions.


AVG() Function

Average returns average value after calculating it from values in a numeric column.

Its general syntax is,

SELECT AVG(column_name) FROM table_name

Using AVG() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query to find average salary will be,

SELECT avg(salary) from Emp;

Result of the above query will be,

avg(salary)
8200

COUNT() Function

Count returns the number of rows present in the table either based on some condition or without condition.

Its general syntax is,

SELECT COUNT(column_name) FROM table-name

Using COUNT() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query to count employees, satisfying specified condition is,

SELECT COUNT(name) FROM Emp WHERE salary = 8000;

Result of the above query will be,

count(name)
2

Example of COUNT(distinct)

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query is,

SELECT COUNT(DISTINCT salary) FROM emp;

Result of the above query will be,

count(distinct salary)
4


FIRST() Function

First function returns first value of a selected column

Syntax for FIRST function is,

SELECT FIRST(column_name) FROM table-name;

Using FIRST() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query will be,

SELECT FIRST(salary) FROM Emp;

and the result will be,

first(salary)
9000

LAST() Function

LAST function returns the return last value of the selected column.

Syntax of LAST function is,

SELECT LAST(column_name) FROM table-name;

Using LAST() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query will be,

SELECT LAST(salary) FROM emp;

Result of the above query will be,

last(salary)
8000

MAX() Function

MAX function returns maximum value from selected column of the table.

Syntax of MAX function is,

SELECT MAX(column_name) from table-name;

Using MAX() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query to find the Maximum salary will be,

SELECT MAX(salary) FROM emp;

Result of the above query will be,

MAX(salary)
10000

MIN() Function

MIN function returns minimum value from a selected column of the table.

Syntax for MIN function is,

SELECT MIN(column_name) from table-name;

Using MIN() function

Consider the following Emp table,

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query to find minimum salary is,

SELECT MIN(salary) FROM emp;

Result will be,

MIN(salary)
6000

SUM() Function

SUM function returns total sum of a selected columns numeric values.

Syntax for SUM is,

SELECT SUM(column_name) from table-name;

Using SUM() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404Scott4410000
405Tiger358000

SQL query to find sum of salaries will be,

SELECT SUM(salary) FROM emp;

Result of above query is,

SUM(salary)
41000


Scalar Functions

Scalar functions return a single value from an input value. Following are some frequently used Scalar Functions in SQL.


UCASE() Function

UCASE function is used to convert value of string column to Uppercase characters.

Syntax of UCASE,

SELECT UCASE(column_name) from table-name;

Using UCASE() function

Consider the following Emp table

eidnameagesalary
401anu229000
402shane298000
403rohan346000
404scott4410000
405Tiger358000

SQL query for using UCASE is,

SELECT UCASE(name) FROM emp;

Result is,

UCASE(name)
ANU
SHANE
ROHAN
SCOTT
TIGER

LCASE() Function

LCASE function is used to convert value of string columns to Lowecase characters.

Syntax for LCASE is,

SELECT LCASE(column_name) FROM table-name;

Using LCASE() function

Consider the following Emp table

eidnameagesalary
401Anu229000
402Shane298000
403Rohan346000
404SCOTT4410000
405Tiger358000

SQL query for converting string value to Lower case is,

SELECT LCASE(name) FROM emp;

Result will be,

LCASE(name)
anu
shane
rohan
scott
tiger

MID() Function

MID function is used to extract substrings from column values of string type in a table.

Syntax for MID function is,

SELECT MID(column_name, start, length) from table-name;

Using MID() function

Consider the following Emp table

eidnameagesalary
401anu229000
402shane298000
403rohan346000
404scott4410000
405Tiger358000

SQL query will be,

SELECT MID(name,2,2) FROM emp;

Result will come out to be,

MID(name,2,2)
nu
ha
oh
co
ig

ROUND() Function

ROUND function is used to round a numeric field to number of nearest integer. It is used on Decimal point values.

Syntax of Round function is,

SELECT ROUND(column_name, decimals) from table-name;

Using ROUND() function

Consider the following Emp table

eidnameagesalary
401anu229000.67
402shane298000.98
403rohan346000.45
404scott4410000
405Tiger358000.01

SQL query is,

SELECT ROUND(salary) from emp;

Result will be,

ROUND(salary)
9001
8001
6000
10000
8000