SQL Functions and its uses

1. SQL Functions
Presented By:
Name - Rohit Kumar
Roll no – 114116066
Dept – Production Engineering

2. SQL – Structured Query Language
 A database computer language designed for the retrieval and management of
data in a relational database.
 All the Relational Database Management Systems (RDMS) like MySQL, MS
Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their
standard database language.
Application –
 Allows users to access data in the relational database management systems.
 Allows users to describe the data.
 Allows users to create and drop databases and tables.
 Allows users to set permissions on tables, procedures and views.
 Allows users to create view, stored procedure, functions in a database.

3. SQL Functions
 What are they?
 SQL functions are simply sub-programs, which are commonly used and re-used
throughout SQL database applications for processing or manipulating data.
 All SQL database systems have DDL (data definition language) and DML (data
manipulation language) tools to support the creation and maintenance of
databases.
 SQL functions are small programs that may have zero or more input parameters
but can return only one value.
 DDL - responsible for tasks related to database creation, modification, and
maintenance.
 DML - responsible for tasks related to the manipulation of data, which
essentially means DML is the programming interface of the database.

4. Classification & Purpose of SQL Function
 Built-in functions -
• Standard functions which are already provided by the SQL database system,
and most of these functions are defined clearly in the ANSI (American
National Standards Institute) SQL standards.
• It is further divided into aggregate functions or scalar functions.
 User-defined functions –
• Functions which are created by the user for a specific purpose.
• It can either return a single value or a set of values.

5. Advantages of Using Functions
 A function needs to be written only once and can be reused multiple times.
This saves time and effort and supports modular programming.
 Functions improve performance and efficiency of the database. SQL functions
are compiled and cached before use.
 Complex programming logic can be decomposed into a number of smaller and
simpler functions, thus making it easier to understand and maintain.

6. Some SQL Function Examples

7. Aggregate Functions
 These functions return a single value after performing calculations on a
group of values.
 Frequently used Aggregate functions –
Function Name Syntax
AVG() SELECT AVG(column_name) FROM
table_name
COUNT() SELECT COUNT(column_name) FROM table-
name
FIRST() SELECT FIRST(column_name) FROM table-
name
LAST() SELECT LAST(column_name) FROM table-
name
MAX() SELECT MAX(column_name) from table-
name
MIN() SELECT MIN(column_name) from table-name
SUM() SELECT SUM(column_name) from table-
name