Uses of SQL

Introduction to Uses Of SQL

SQL or Structured Query Language is specifically used by business professionals or program developers for administering, updating, maintaining and manipulating the databases or tables that are used for business decision-making. It is usually used to fetch data, update the contents of the table, or operate on the structure of the database or tables, using any type of database tools, which will have a user interface to apply the operations on the database. SQL can be used for both relational and multidimensional types of databases. SQL is a declarative language which means it is a programming paradigm, a style of building the structure and elements of computer programs that express the logic of a computation without describing its control flow.

Some of the famous Databases are listed below:

Uses OF SQL

Examples given below are based on dummy table with table name “student_records” having columns id, name, address, and mobile.

Constraints: “id” is used as the primary key of the table and one more column with name “mobile” and this column contains only unique data;

1. DQL

It stands for Data Query Language. It is used to retrieve data from the database.

The SQL statement is SELECT.

Example:

SELECT * from student_records;

2. DDL

It stands for Data Definition Language. This is used to define database schema, thus it deals with the description of database schema and is used to create and modify the structure of database objects in the database. Thus the SQL statements are CREATE, DROP, ALTER, TRUNCATE, COMMENT, RENAME.

Example:

CREATE TABLE student_records
(id integer NOT NULL DEFAULT,
name character varying,
address character varying,
mobile numeric,
CONSTRAINT student_records_pkey PRIMARY KEY (id)
)
DROP TABLE student_records;
ALTER TABLE student_records ALTER COLUMN mobile character varying;

3. DML

It stands for Data Manipulation Language. It is used to store, modify, delete and update data in the database. Thus the SQL statements are INSERT, UPDATE and DELETE.

Example:

INSERT into student_records values (1,”name”,”address”, mobile);
UPDATE student_records set address = “new address” where name= “name”;
DELETE from student_records where mobile = [enter_mobile_number];
TRUNCATE table student_records;

4. DCL

It stands for Data Control Language. It is used to grant access to data stored in the database.

SQL statements are GRANT and REVOKE.

Syntax:

REVOKE privilege_name
On object_name
From {user_name | PUBLIC | role_name};
GRANT privilege_name
On object_name
To {user_name | PUBLIC | role_name}
[WITH GRANT OPTION];

**NOTE: To use GRANT command specific role_name should be created first.

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5. Database Transaction Management

Transaction Management means to maintain the transaction related to the database i.e. following the basic rules for ACID properties of the database. The transaction has only two results i.e. either success or failure. Thus the SQL Statement is TRANSACTION, COMMIT, ROLLBACK, SAVEPOINT.

6. Procedures, User-defined Functions, Triggers, Indexes, and others

We can write procedures, user-defined functions, triggers, indexes, cursors as per the requirements which is nothing but SQL statements to make our work easy to meet the business requirements.

7. Reporting Purpose

SQL queries are very important from report perspective which every project have. We can write queries for standalone reports also for fetching data for the report.

8. Manual Analysis

SQL queries are very important for analysis when manual interventions are necessary. With the uses of SQL queries we can filter out the necessary data from the structured data and it could be used for analysis.

9. SQL with NTC Hosting

Even the MySQL hosting service provides the ability for the construction of big and powerful websites, web-based applications and programs. MySQL open source database solution and insist on speed, stability and scalability, then MySQL hosting solution is needed.

10. SQL Join

A SQL join is an instruction to combine data from two sets of data (i.e. two or more tables).

• (INNER) JOIN: Returns matching values in both tables as output.
• LEFT (OUTER) JOIN: It returns all records of the left table and the matching records of the right table as output.
• RIGHT (OUTER) JOIN: It returns all records 0f the right table, and the matching records of the left table as output.
• FULL (OUTER) JOIN: It returns all records if there is a match in either of the table i.e. left or right.

11. SQL Union:

The result-set of two or more SELECT statements can be joined by UNION.

12. SQL Wildcards:

A wildcard character is a special character in SQL which are used to substitute any other character(s) in a string.

SQL Wildcard Operators:  ‘%’ and ‘_’ are called wildcards operators.

NOTE:

• % – Representing zero, one, or multiple characters in a character value ( used while filtering).
• _ – Representing a single character.

Conclusion

So it can be concluded at the end that even today with the fast-growing technologies and evolution of no SQL databases in the market, Uses of SQL still plays an important role for structured data. SQL provides flexibility of querying the tabular data with SQL queries which is a great help in many ways.

Recommended Articles

This has been a guide to Uses of SQL. Here we have explained the basic concept and different uses of SQL with examples. You may also look at the following articles –

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3. Cheat Sheet MySQL
4. Careers in SQL Server