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What is PostgreSQL and Why is it so Useful?

This article focuses on one of the most useful and important databases in the IT industry and that is PostgreSQL. This open-source database is an advanced, enterprise-class relational database that supports SQL (relational) and JSON (non-relational) queries. This database management system has been developed by its community for over 20 years, which has contributed to its high levels of accuracy, integrity, and resilience. Many web, mobile, geospatial, and analytics applications utilize PostgreSQL as their primary data store or warehouse. A key feature of PostgreSQL is that it supports advanced data types, and it offers performance optimizations that are comparable to those found in commercial database systems like Oracle and SQL Server.

What is PostgreSQL?

PostgreSQL (a.k.a “Postgres”) is a relational database management system (ORDBMS) that emphasizes extensibility and compliance with standards. The main purpose of a database server is to store data securely and support best practices. And retrieve it later, as requested by other applications, whether they are running on the same computer or on another computer across a network. A recent version also offers replication of the database itself for security and scalability. This makes it suitable for applications ranging from single-machine applications with few concurrent users to large internet-facing applications with many concurrent users.

Using multi-version concurrency control (MVCC), PostgreSQL avoids locking issues, is ACID-compliant, transactional (including most DDL statements), provides immunity to dirty reads, and is fully serializable. SQL:2011 is the most common standard. It is ACID-compliant and transactional (including most DDL statements). It handles complex SQL queries with many indexing techniques not available in other databases. Has triggers, views, and foreign keys.

Postgres has the ability to work with all major proprietary and open source databases. Additionally, it supports migration from them with its extensive standard SQL support and migration tools. Furthermore, if proprietary extensions had been used, the extensibility of this software can emulate many through built-in and third-party open source compatibility extensions, such as Oracle’s.

Postgres History

As a result of Professor Michael Stonebreaker’s leadership at Berkeley, the Postgres project started in 1986. They entitled it POSTGRES in Berkeley, which was the successor of its older version “Ingres” which was another product of the same place. In order to fully support multiple data types, POSTGRES developers designed it with the fewest features possible. In 1996, they renamed it PostgreSQL to illustrate its support for the SQL querying language (although PostgreSQL is still commonly abbreviated as Postgres). PostgreSQL is an open-source database project whose contributors – the PostgreSQL Global Development Group – continue to make regular major and minor releases.

PostgreSQL Use Cases

Geospatial database

As a geospatial data store, PostgreSQL can be used with PostGIS to support location-based services and geographic information systems (GIS).

LAPP open source stack

The PostgreSQL database can run dynamic websites and apps as an alternative to the LAPP stack (LAPP stands for Linux, Apache, PostgreSQL, PHP, Python, and Perl);

General purpose OLTP database

For internet-scale applications, solutions, and products, startups and large enterprises alike use PostgreSQL as their primary data store.

Federated hub database

The Foreign Data Wrappers and JSON support make Postgres a federated hub for polyglot databases, including NoSQL.

The Features of PostgreSQL

There are many advanced features in PostgreSQL that are not available in other enterprise-class database management systems, including:

1. Sophisticated locking mechanism
2. Nested transactions (savepoints)
3. Multi-version concurrency control (MVCC)
4. Asynchronous replication
5. User-defined types
6. Foreign key referential integrity
7. Table inheritance
8. Native Microsoft Windows Server version
9. Tablespaces
10. Point-in-time recovery
11. Views, rules, subquery

PostgreSQL vs. MySQL

MySQL and Postgres both have been around for decades. Despite all their similarities, PostgreSQL and MySQL have a number of characteristics that set them apart from each other, as we will see. They’re both secure RDBMSes with clustering capabilities and network fault tolerance.

Architecture

The difference between Postgres and MySQL is that Postgres has object-relational capabilities, while MySQL has purely relational capabilities. This makes using PostgreSQL more difficult, but it also makes using PostgreSQL less complex. MySQL provides 16 different storage engines suitable for different use cases. InnoDB is the default storage engine, providing index-organized tables.

PostgreSQL has a single, ACID-compliant storage engine. Each client connection PostgreSQL establishes generates its own memory allocation, so it needs a lot of memory on systems with many connections. MySQL uses a single process and maintains one thread (or execution path) per connection, which is sufficient for most applications that do not exceed enterprise scope. PostgreSQL supports materialized views, which can improve performance for complex queries, and is more robust when it comes to views, triggers, and stored procedures.

SQL INSERT, UPDATE, and DELETE statements are supported by both databases with AFTER and BEFORE triggers. Postgres also provides an INSTEAD OF trigger, which allows complex SQL statements to be executed within a trigger using functions. Postgres offers the ability to call procedures written in languages other than SQL as well as standard SQL stored procedures.

Data Types

A PostgreSQL database offers a wider variety of data types than MySQL. if your application uses any of its unique data types or unstructured data, it may be a better choice. both databases will work if you only need basic character and numeric data types.

Indexes

As your data grows, you can fine-tune your database performance by picking from multiple indexing options to get faster query responses from your database and a better user experience for your application users.

Security

Both databases support user and group management and grant SQL privileges to roles. PostgreSQL supports IP-based client filtering and authentication using PAM and Kerberos, while MySQL supports PAM, native windows services, and LDAP for user authentication. In terms of security, the two databases have comparable options.

Support and Documentation

Due to the fact that Postgres is not developed by a company, it lacks support engineers, but its community support forums are exceptionally good. you can judge each vendor’s availability of documentation yourself since it can be found online. MySQL offers similar forums, as well as Oracle’s paid support plans.

Wrapping Up

In this article, you learned about the PostgreSQL database which is also called Postgres. Also, you got familiar with its use cases and features and its comparison to the MySQL database. Generally, choosing a database management system when starting a new project is an afterthought. Frameworks usually come with some kind of object-relational mapping tool (ORM), which makes them all equally slow and hides the differences between the platforms. A good developer must always make informed decisions among the different options, weighing the benefits and disadvantages of each. Don’t fall into the trap of familiarity and comfort – don’t fall into the trap of comfort and familiarity.

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What is SQL Injection and How should we Prevent it?

The SQL injection attack involves manipulating backend databases with malicious SQL code in order to gain access to information that wasn’t meant to be displayed. This information includes sensitive company data, user lists, and private customer information. A successful SQL injection can have a far-reaching impact on a business. In some cases, an attacker may gain administrative rights to a database if they successfully view user lists, delete entire tables, or gain access to entire databases. These things are highly detrimental to a company. If personal information, such as phone numbers, addresses, and credit card numbers, is stolen, it can result in the loss of customer trust. SQLi can be used to attack any SQL database, but websites tend to be the most common targets.

How do we query from SQL?

A SQL query is a query that executes commands, such as retrieving data, updating records, and removing records. SQL is a standardized language for accessing and manipulating databases; We use it to build personalized data views for each user. And execute these tasks by different SQL elements, for example, queries implementing the SELECT statement to retrieve data according to user-provided parameters. Generally, We query data from a database as below:

SELECT CustomerName, CustomerEmail
FROM Customer
WHERE CustomerNumber = CustomerNumber


From this, the web application builds a string query that is sent to the database as a single SQL statement:

sql_query= "
SELECT CustomerName, CustomerEmail
FROM Customer
WHERE CustomerNumber = " & Request.QueryString("CustomerID")


A user-provided input http://www.ShoppingCenter.com/customer/customers.asp?customerid=78 can then generate the following SQL query:

SELECT CustomerName, CustomerEmail
FROM Customer
WHERE CustomerNumber = 78


As you can see from the code, this query provides the name and email of customer number 78.

Different Kinds of SQL Injection:

You can classify SQL injections based on their methods of accessing backend data and their damage potential. There are three types of SQL injections: In-band SQLi (Classic), Inferential SQLi (Blind), and Out-of-band SQLi.

In-band SQLi

An SQLi attack that uses the same channel of communication for both launching and gathering results is called an in-band SQLi attack, which is simple and efficient. It has two subvariations:

Error-based SQLi

A database attack occurs when the attacker causes it to produce error messages. The attacker can potentially use the data provided by these errors to gather information about the database structure. The attacker can alter the SQL commands by exploiting incorrectly filtered characters, including semicolons which we use in order to separate two fields. The below example illustrates how the attacker can delete the entire user database:

SELECT ItemName, CustomerEmail
FROM Customers
WHERE CustomerNumber = 78; DROP TABLE USERS


As you can see the semicolon creates an error, resulting in the execution of the DROP TABLE USERS command.

Union-based SQLi

In this technique, the attacker uses the UNION SQL operator to assemble multiple select statements generated by the database into a single HTTP response. The response may contain data that can be exploited. UNION SELECT statement combines two unrelated SELECT queries to retrieve data from different database tables. You can the example below:

SELECT CustomerName, CustomerEmail
FROM Customers
WHERE CustomerID = '78' UNION SELECT Username, Password FROM Users;


This query makes use of the UNION SELECT statement to combine the name and email of customer 78 with names and passwords for all users.

Inferential (Blind) SQLi

In order to understand the server’s structure, the attacker sends data payloads to it and observes its behavior and response. Due to the fact that the website database transfers no data to the attacker, the attacker cannot see information about the attack in-band. As a result of their reliance on the response or behavior of the server, blind SQL injections are typically slower to execute but may be equally damaging. Blind SQL injections can be any one of the following types:

Boolean:

In boolean SQLi, The attacker sends a SQL query to the database, asking the application to return a result. Depending on whether the query is true or false, the information within the HTTP response will change or remain unchanged. By analyzing the response, the attacker can determine whether it generated a true or false result.

Time-based:

In a time-based SQLi, As the attacker sends a SQL query to the database, the database waits (for a period of a few seconds) before it can respond. The attacker can determine whether a query is true or false by the time the database takes to respond. If the message returned true or false, an HTTP response will be generated instantly or after a waiting period. Therefore, the attacker does not need to rely on database data.

Out-of-band SQLi:

An attacker can only conduct this type of attack if certain features of the database server used by the web application are enabled. this form of attack is primarily used to replace in-band and inferential SQLi attacks. When the attacker is unable to use the same channel to launch the attack and gather information, or when the server is too slow or unstable for this to take place, out-of-band SQLi is used. These techniques rely on the server’s ability to create DNS or HTTP requests to transfer data to an attacker.

How to Prevent SQL Injection Attacks:

The first step in preventing SQLI attacks is input validation (or sanitization), which is the process of writing code that detects illegitimate inputs. Though input validation is always a good practice, it is rarely foolproof. The reality is that, in most cases, it is simply not feasible to map out all legal and illegal inputs-at least not without causing a large number of false positives, which interfere with the user experience and the functionality of the application.

It is for this reason that web application firewalls (WAFs) are commonly used to block SQLI attacks and other online threats. To perform this task, a WAF typically relies on a large, and constantly updated, list of meticulously crafted signatures that allow it to surgically weed out malicious SQL queries. The signatures in such a list usually address specific attack vectors, and they are regularly patched so that newly discovered vulnerabilities can be blocked. Additionally, modern web application firewalls often integrate with other security solutions. These firewalls do this by allowing them to receive additional information that will further enhance their security.

Wrapping Up:

In this article, you got familiar with one of the most important subjects in web security and SQL-based databases known as SQLi (SQL Injection). Furthermore, you learned about the different types of SQL Injection attacks with some examples for some of them. In the end, we talked about the ways you can follow to prevent these attacks.

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