SQL Injection Testing Tutorial (Example and Prevention of SQL Injection Attack)

SQL Injection Examples and ways to prevent SQL Injection Attacks on Web Applications

While testing a website or a system, the tester's aim is to ensure if the tested product is as much protected, as possible.

Security Testing is usually performed for this purpose. In order to perform this type of testing, initially, we need to consider, which attacks are most likely to happen. SQL Injection is one of those attacks.

SQL Injection Attach Example and Prevention

SQL Injection is considered as one of the most common attacks as it can bring serious and harmful consequences to your system and sensitive data.

What Is SQL Injection?

Some of the user inputs might be used in framing SQL Statements that are then executed by the application on the database. It is possible for an application NOT to handle the inputs given by the user properly.

If this is the case, a malicious user could provide unexpected inputs to the application that are then used to frame and execute SQL statements on the database. This is called SQL Injection. The consequences of such an action could be alarming.

As the name itself implies, the purpose of the SQL Injection attack is to inject the malicious SQL code.

Each and every field of a website is like a gate to the database. In the login form, the user enters the login data, in the search field the user enters a search text, in the data saving form the user enters data to be saved. All these indicated data goes to the database.

Instead of correct data, if any malicious code is entered, then there are possibilities for some serious damage to happen to the database and the whole system.

SQL Injection is performed with the SQL programming language. SQL (Structured Query Language) is used for managing the data held in the database. Therefore during this attack, this programming language code is being used as a malicious injection.

This is one of the most popular attacks, as databases are used for almost all the technologies.

Many applications use some type of Database. An application under test might have a user interface that accepts user input that is used to perform the following tasks:

#1) Show the relevant stored data to the user e.g. the application checks the credentials of the user using the login information entered by the user and exposes only the relevant functionality and data to the user

#2) Save the data entered by the user to the database e.g. once the user fills up a form and submits it, the application proceeds to save the data to the database; this data is then made available to the user in the same session as well as in subsequent sessions

Risks Of SQL Injection

Nowadays, a database is being used for almost all the systems and websites, as data should be stored somewhere.

As sensitive data is being stored in the database, there are more risks involved in the system’s security. If any personal website or blog’s data would be stolen, then there won’t be much damage when compared to the data that would be stolen from the banking system.

The main purpose of this attack is to hack the system’s database, therefore this attack’s consequences can really be harmful.

The following things might result from SQL Injection

  • Hacking other person’s account.
  • Stealing and copying website’s or system’s sensitive data.
  • Changing the system’s sensitive data.
  • Deleting system’s sensitive data.
  • The user could log in to the application as another user, even as an administrator.
  • The user could view private information belonging to other users e.g. details of other users’ profiles, transaction details, etc.
  • The user could change application configuration information and the data of the other users.
  • The user could modify the structure of the database; even delete tables in the application database.
  • The user could take control of the database server and execute commands on it at will.

The above-listed risks can really be considered serious, as restoring a database or its data can cost a lot. It can cost your company a reputation and money to restore the lost data and system. Therefore it is highly recommended to protect your system against this type of attack and consider Security Testing as a good investment in your product’s and company’s reputation.

As a tester, I would like to comment, that testing against possible attacks is a good practice even if Security Testing was not planned. This way you can protect and test the product against unexpected cases and malicious users.

The Essence Of This Attack

As mentioned earlier, the essence of this attack is to hack the database with malicious purpose.

In order to perform this Security Testing, initially, you need to find the vulnerable system parts and then send malicious SQL code through them to the database. If this attack is possible for a system, then appropriate malicious SQL code will be sent and harmful actions may be performed in the database.

Each and every field of a website is like a gate to the database. Any data or input that we usually enter in any field of the system or website goes to the database query. Therefore, instead of correct data, if we would type any malicious code, then it may be executed in the database query and bring harmful consequences.

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For performing this attack, we have to change the act and purpose of an appropriate database query. One of the possible methods to perform it is to make the query always true and after that insert your malicious code. Changing the database query to always true can be performed with simple code like ‘ or 1=1;–.

Essence of SQL Injection

Testers should keep in mind, that while checking if changing the query to always true can be performed or not, different quotes should be tried – single and double. Therefore, if we have tried code like ‘ or 1=1;–, we should also try the code with double quotes “ or 1=1;–.

Essensce of SQL Injection

For Example, let's consider that we have a query, that is searching for the entered word in the database table:

select * from notes nt where nt.subject = ‘search_word‘;

Therefore instead of the search word, if we enter a SQL Injection query ‘ or 1=1;–, then the query will become always true.

select * from notes nt where nt.subject = ‘ ‘ or 1=1;–

In this case, the parameter “subject“ is closed with the quote and then we have code or 1=1, which makes a query always true. With the sign “–“ we comment on the rest of the query code, which will not be executed. It is one of the most popular and easiest ways to start controlling the query.

Few other codes may also be used to make the query always true, like:

  • ‘ or ‘abc‘=‘abc‘;–
  • ‘ or ‘ ‘=‘ ‘;–

The most important part here is that after comma sign we can enter any malicious code, that we would like to be executed.

For Example, it may be ‘ or 1=1; drop table notes; —

Drop Table Notes

If this injection is possible, then any other malicious code may be written. In this case, it will only depend on the malicious user's knowledge and intention. How to Check SQL Injection?

Checking for this vulnerability can be performed very easily. Sometimes it is enough to type ‘ or “ sign in the tested fields. If it returns any unexpected or extraordinary message, then we can be sure, that SQL Injection is possible for that field.

For Example, if you get an error message like ‘Internal Server Error‘ as a search result, then we can be sure, that this attack is possible in that part of the system.

Other results, that can notify possible attack include:

  • Blank page loaded.
  • No error or success messages – functionality and page do not react to the input.
  • Success message for malicious code.

Let's look around at how this works in practice.

For Example, Let's test if an appropriate login window is vulnerable for SQL Injection. For this purpose, in the email address or password field, we just type sign as shown below.

Email Address

If such input returns result like error message ‘Internal Server Error‘ or any other listed inappropriate result, then we can almost be sure, that this attack is possible for that field.

Internal Server Error

A  very tricky SQL Injection code may also be tried. I would like to mention, that in my career I have not encountered any case when there was ‘Internal Server Error' message as a result of the sign, but at times the fields did not react for more complicated SQL code.

Therefore checking for SQL Injection with a single quote ‘ is quite a trustworthy way to check if this attack is possible or not.

If the single quote does not return any inappropriate result, then we can try to enter double quotes and check the results.

Single Quote

Also, SQL code for changing the query to always true can be considered as a way to check if this attack is possible or not. It closes the parameter and changes the query to ‘true‘. Therefore if not being validated, such input can also return any unexpected result and inform the same, that this attack is possible in this case.

Essensce of SQL Injection

Checking for possible SQL attacks can also be performed from the website‘s link. Suppose we have a website‘s link as http://www.testing.com/books=1. In this case ‘books‘ is a parameter and ‘1‘ is its value. If in the provided link we would write ‘ sign instead of 1, then we would check for possible Injection.

Therefore link http://www.testing.com/books= will be like a test if the SQL attack is possible for the website http://www.testing.com or not.

Testing Link

In this case, if link http://www.testing.com/books= returns an error message like ‘Internal Server Error‘ or a blank page or any other unexpected error message, then also we can be sure, that SQL Injection is possible for that website. Later, we can try to send more tricky SQL code through the website‘s link.

To check if this attack is possible through the website‘s link or not, code like ‘ or 1=1;– can also be sent.

Testing Links

As an experienced software tester, I would like to remind, that not only the unexpected error message can be considered as a SQL Injection vulnerability. Many testers check for possible attacks only in accordance with error messages.

However, it should be remembered, that no validation error message or success message for malicious code can also be a sign, that this attack is possible.

Security Testing Of Web Applications Against SQL Injection

Security testing of web applications explained with simple examples:

Since the consequences of allowing this vulnerability technique could be severe, it follows that this attack should be tested during the security testing of an application. Now with an overview of this technique, let us understand a few practical examples of SQL injection.

Important: This SQL Injection Test should be tested only in the test environment.

If the application has a login page, it is possible that the application uses dynamic SQL such as the statement below. This statement is expected to return at least a single row with the user details from the Users table as the result set when there is a row with the username and password entered in the SQL statement.

SELECT * FROM Users WHERE User_Name = ‘” & strUserName & “‘ AND Password = ‘” & strPassword & “’;”

If the tester would enter John as the strUserName (in the textbox for username) and Smith as strPassword (in the textbox for password), the above SQL statement would become:

SELECT * FROM Users WHERE User_Name = 'John' AND Password = 'Smith’;

If the tester would enter John’– as strUserName and no strPassword, the SQL statement would become:

SELECT * FROM Users WHERE User_Name = 'John'-- AND Password = 'Smith’;

Note that the part of the SQL statement after John is turned into a comment. If there were any user with the username of John in the Users table, the application could allow the tester to log in as the user John. The tester could now view the private information of the user John.

What if the tester does not know the name of any existing user of the application? In such a case, the tester could try common usernames like admin, administrator, and sysadmin. If none of these users exists in the database, the tester could enter John’ or ‘x’=’x as strUserName and Smith’ or ‘x’=’x  as strPassword. This would cause the SQL statement to become like the one below.

SELECT * FROM Users WHERE User_Name = 'John' or 'x'='x' AND Password = 'Smith’ or ‘x’=’x’;

Since ‘x’=’x’ condition is always true, the result set would consist of all the rows in the Users table. The application could allow the tester to log in as the first user in the Users table.

Important: The tester should request the database administrator or the developer to copy the table in question before attempting the following attacks.

If the tester would enter John’; DROP table users_details;’—as strUserName and anything as strPassword, the SQL statement would become like the one below.

SELECT * FROM Users WHERE User_Name = ‘John’; DROP table users_details;’ –‘ AND Password = 'Smith';

This statement could cause the table “users_details” to be permanently deleted from the database.

Though the above examples deal with using the SQL injection technique only the login page, the tester should test this technique on all the pages of the application that accept user input in textual format e.g. search pages, feedback pages, etc.

SQL injection might be possible in applications that use SSL. Even a firewall might not be able to protect the application against this technique.

I have tried to explain this attack technique in a simple form. I would like to re-iterate this attack should be tested only in a test environment and not in the development environment, production environment or any other environment.

Instead of manually testing whether the application is vulnerable to SQL attack or not, one could use a Web Vulnerability Scanner that checks for this vulnerability.

Related reading: Security testing of the Web Application. Check this for more details on different web vulnerabilities.

Vulnerable Parts Of This Attack

Before starting the testing process, every sincere tester should more or less know which parts would be most vulnerable to possible this attack.

It is also a good practice to plan which field of the system is to be tested exactly and in what order. In my testing career, I have learned, that it is not a good idea to test fields against SQL attacks randomly as some fields can be missed.

As this attack is being performed in the database, all data entry system parts, input fields, and website links are vulnerable.

Vulnerable parts include:

  • Login fields
  • Search fields
  • Comment fields
  • Any other data entry and saving fields
  • Website‘s links

It is important to notice that while testing against this attack it is not enough to check only one or a few fields. It is quite common, that one field may be protected against SQL Injection, but then another does not. Therefore it is important not to forget to test all the website’s fields.

Automating SQL Injection Tests

As some tested systems or websites can be quite complicated and contain sensitive data, testing manually can be really difficult and it takes a lot of time too. Therefore testing against this attack with special tools can be really helpful at times.

One such SQL Injection tool is SOAP UI. If we have automated regression tests at the API level, we can also switch checking against this attack using this tool. In the SOAP UI tool, there are already prepared code templates for checking against this attack. Those templates can also be supplemented by your own written code.

It is a quite reliable tool.

However, a test should already be automated at the API level, which is not that easy. Another possible way to test automatically is by using various browser plugins.

It should be mentioned, that even if automated tools save your time, they are not always considered to be very reliable. If we are testing a banking system or any website with very sensitive data, it is highly recommended to test it manually. Where you can see the exact results and analyze them. Also, in this case, we can be sure, that nothing was skipped.

Comparison With Other Attacks

SQL Injection can be considered as one of the most serious attacks, as it influences the database and can make serious damage to your data and the whole system.

For sure it can have more serious consequences than a Javascript Injection or HTML Injection, as both of them are performed on the client-side. For comparison, with this attack, you can have access to the whole database.

It should be mentioned, that to test against this attack, you should have quite good knowledge of SQL programming language and in general, you should know how databases queries are working. Also while performing this injection attack you should be more careful and observant, as any inaccuracy can be left as SQL vulnerabilities.


I hope you would have got a clear idea of what a SQL Injection is and how should we prevent these attacks.

However, it is highly recommended to test against this type of attack every time when a system or website with a database is being tested. Any left database or system vulnerabilities can cost a company‘s reputation and a lot of resources to restore the whole system.

As testing against this injection helps to find the most important security vulnerabilities, it is also recommended to invest in your knowledge and testing tools.

If Security Testing is planned, then testing against SQL Injection should be planned as one of the first testing parts.

Have you come across any typical SQL Injection? Feel free to share your experiences in the comments section below.

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93 thoughts on “SQL Injection Testing Tutorial (Example and Prevention of SQL Injection Attack)”

  1. SQL injection is ignored testing part in most of the companies. But as developers don’t pay attention on database security. its testers responsibility to secure application against such attacks. Take this responsibility.

    Thanks for this article.

  2. This article is very much useful for the users who were interested to start sql injection. Thanks for this great work and keep going ..

  3. Nice Article By Inder P Singh. I was aware of the Sql injection methodology but I was not sure about the implementation.. Thess Example are great releif for the Web and desktop application tester..

    Many Many thaks to Inder. Hope to hear from you soon on “URL Re-Writing”. This is another security threat for web based application.

  4. Hello Vijay,

    But under testing, for e.g for login page

    If the user is not allowed to enter any character other than alphabets and numbers in username and password fields.

    Would it be enough to stop the SQL injection attack by putting validations on special chars, blank spaces and null values.

  5. @Yogni,

    There are two reasons why the approach of disallowing any characters other than alphabets and numbers might not work:

    1. Some web applications allow users to create usernames containing other characters e.g. a user is allowed to use an email address as a username, a user might use a user name with an apostrophe like O Brien.

    Further, passwords with special characters are encouraged since the number of permutations of such passwords increases. This makes it more difficult for an attacker to guess a password.

    2. Even if characters other than alphabets and numbers are not allowed on client-side, the attacker might intercept the HTTP traffic between the browser and the server with the help of tools like TamperIE, Fiddler etc and insert the special characters that were prevented in the client-side validation.

    Hope this helps!
    Inder P Singh

  6. @Rajesh,

    That is a good question. Not one but many tools and web vulnerability scanners are available to test SQL attack. However, when using a tool or a scanner, it is best to complement the test with manual testing because the tool or scanner might have limited features available.

    Inder P Singh

  7. Hello Mr.Inder P Singh

    So according to you what should be the test cases for testing these two text fields.

    You told about allowing the special character under for password , that’s very true since all the bank forcefully suggest to keep the A/c password with some complex combination of chars, special chars & numbers.

    Because here the security issue is on top priority, so under these circumstances what should the various test cases and test plans.


    (software test engineer)

  8. Hi,
    “Software testing help” is highly helpful for me. I have a doubt, what will be the first deliverable from a tester side after getting the SRS of a project? whether integration test case or System test case or understanding document. As of now we are preparing a Understanding document then System test case for entire requirement. Please clear my doubt.

    Thanks & Regards

  9. Nice article!
    But I’m not agree with the first comment:

    “its testers responsibility to secure application against such attacks. Take this responsibility.”

    I think the correct way to say is:

    “Its testers responsability to run SQL attack testCases; the whole team must take the responsibility to secure application againts such attacks”

    Maybe is only a word puzzle, but as testers we need to emphasize that the Quality is matter of all the team, not only the testers


  10. Hello, i have a question. Does anybody know how to do security testing on a web base application using QTP?. If so can you pls e-mail me or contact me. I really do need to know about the security testing and how i go about it. e-mail: kajohnson00@gmail.com


  11. @Rajesh,

    There are many tools available to test this attack. Examples of such tools include web vulnerability scanners.
    1. It might be better to choose a new tool (that checks for exploits discovered recently.)
    2. You might want to use multiple tools that complement each other.
    3. Instead of limiting yourself to the capabilities of the available tools, you might want to supplement testing with manual testing for SQL attack.


    Testing for this attack would depend on the following:
    1. The flavor of SQL used by the application
    2. The kind of query the application uses on the log in page
    3. Results of the previous test

    Here are a few test ideas that are based on the examples given in the article:
    1. Check if entering an apostrophe character causes a SQL error in the application.
    2. Guess a common user name and enter it in the field of user name along with a string terminator and a comment character e.g. —
    3. Enter any user name along with a condition that is always true.

    I will explain more test ideas in a future article.

    Thank you both,
    Inder P Singh

  12. @Moesha,

    You are right. If any problem related to this vulnerability has been found in the application, it would make sense to have automated tests to check the same in other areas of the application as well as in future releases of the application. However, keep in mind that execution of some test cases would depend on the success of the prior test case(s).

    Thank you,
    Inder P Singh

  13. please anyone answer to below mentioned java script, which is a web site hacking script.

    How to handle this java script in DB.

    Thanks in advance……….

  14. very nice article i am working as SQA i am interested in learning testing skills and i recently heard about this attack and testing that is explained very clearly.
    thank you .

  15. very nice article i am working as SQA i am interested in learning testing skills and i recently heard about this attack and testing that is explained very clearly.
    thank you .“Software testing help” is highly helpful for me.
    If there is a proper code then it will be better.

  16. Magic String:–The magic string is a simple string of SQL used primarily at login pages. The magic string is
    When used at a login page, you will be logged in as the user on top of the SQL table.

  17. Really, this article is very good to understand the concept of SQL attack. After reading the example of this attack, I got very clear about the concept
    Very nice article….Hope U would write more article with Examples..

  18. i Dont think this attack is neccessary as part of testing for all the web Applications.but it should be made part of test plan depending type of data it is dealing with say crucial personnel information which is high importance to the user say a gov website.In all usch cases it should be made part of testplan if needed

  19. @Ravishankar,

    Security testing deals with not only the senstivity of information (as the crucial personnel information mentioned by you), it also deals with the availability of information. Therefore, if you have a web application that does not have any sensitive information but allows an attacker to gain control of the application/ database using this vulnerability technique, the attacker could cause a denial of service to the users. This means that all web applications could be benefited from security testing using the SQL attack technique.

    Thanks for your comment!
    Inder P Singh

  20. @Inder: If I understood correctly, if the application is set to trow an error page (something like “An error has ocurred. Please contact your admin”) it greatly reduces the risk of such attacks?


  21. @Vlad,

    An error page NOT containing the SQL error is better than the one that does because it does not help the attacker with further information. However, such a design may not reduce the risk of SQL attacks; it may simply increase the time required for the attack. This post is about testing a web application with this attack technique but is not about ways to secure the application against this attack technique.

    Even though you have asked a simple question, I somehow get the feeling that you are quite knowledgeable about this vulnerability. If so, would you like to share some of your knowledge on this topic?

    Many thanks for your comment!
    Inder P Singh

  22. Can i know how can i use this attack when hibernate querying is used. As in HQL the query is dynamically generated and these specials characters are not allowed as there are validations to it.

  23. @inder
    In one of ur previous posts you were talking abt attacking HTTP request before it reach to server, If i am not wrong this is CSS (Cross site Scripting) I used a tool Web Scrab to test the same where in i can stop the user entered parameters and i can pass my own parameters to the server. But during this process i faced a problem like we used HQL in the project where if i enter any invalid charecters then even though there is no validation but hibernate is throwing an Invalid Query exception. Is there any tools or mechanism where in i can break the HQL?

  24. hi all,

    I am creating a web app scanner for my major project for 4th year B.E in CSE.I need help in finding the right tools and technologies for its implementation.Some one can help me….

  25. Deepak,

    You should consider any one or more of Perl, Python or PHP programming languages to build your scanner. It would be well to be on the lookout for existing components that are available for you to use.

    Inder P Singh

  26. hi to all,
    am testing a web application with database for security testing, its username and password is username = admin
    password = admin..can you tell me sql attack for this application?

  27. @Raja,

    Thank you for your question!

    You should try out various combinations of the username and the password as partial SQL expressions to see if your application is susceptible to SQL attack. Some examples are:
    1. Any name followed by an apostrophe
    2. admin followed by an apostrophe
    3. Username as John’ or ‘x’=’x and password as Smith’ or ‘x’=’x

    Happy testing!
    Inder P Singh

  28. hi,
    i have an application which is having a login page.How can we determine that the login credentials are not hard coded and it is really checking with the database entries to allow the login.
    Please reply

  29. hi venkat,

    Suppose I have an e commerce web site.
    So if you want to buy something you have to login with your credentials and if the the data you are giving is existing the DB,then only you will access to the next page.
    Consider the name pooja is not in DB.So if i am giving the name as pooja,login should fail.
    In this case let us take the case that the developer is coded like if username=”pooja” then allow(I dont knw programming,i m just giving the algorthm).Here if when you are giving the name as pooja,eventhough the name is not existing in the DB,it will allow you to go to the next page,since it is hard coded.
    Here my question is as a tester how can we determine that the validation is really happening with the database and the name is not hard coded.

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