How Do Prepared Statements Protect Against SQL Injection?

Prepared Statements: Your Shield Against SQL Injection

SQL injection vulnerabilities arise when user-supplied data is improperly integrated into SQL queries, allowing attackers to manipulate the query's logic. Prepared statements offer a robust defense by separating the SQL query structure from the data values.

The process works in two phases:

1. Query Compilation: The database receives the parameterized query, a pre-compiled statement containing placeholders instead of direct data values (often represented as "?"). For example:

$db->prepare("SELECT * FROM users WHERE username = ?");

2. Data Binding: The actual data values are sent to the database separately using a dedicated function (like $db->execute($data)).

This separation is crucial. Because the data is handled independently, it cannot be interpreted as executable code, preventing SQL injection attacks.

Important Note: Prepared statements effectively protect only data literals. They do not safeguard against vulnerabilities stemming from dynamically constructed parts of the query, such as column or table names. For such scenarios, consider implementing additional security measures, such as input validation and whitelisting.

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