A guide to SQL injection

SQL injection is a malicious technique that is meant to compromise or destroy databases. It is one of the most common web-hacking techniques.

SQL injection is performed by placing malicious code in SQL statements via an input.

The following example is a code snippet that will retrieve a user from a database based on an AccountId .

passedInAccountId = getRequestString("AccountId");
sql = "select * from Accounts where AccountId = " + passedInAccountId;

SQL injection can be used to compromise this code by injecting a 1=1; statement for AccountId .

https://www.foo.com/get-user?AccountId="105 OR 1=1;"

1=1 will always evaluate to TRUE . This will cause the executed code to output all of the Accounts table.