What are Prepared Statements and why are they used

Prepared Statements are a way to execute SQL queries against relational databases. This technique is used to improve security, efficiency, and code clarity when compared to building dynamic SQL queries by concatenating strings.

Here are the main features and reasons for using Prepared Statements.

Security against SQL Injection

Using Prepared Statements helps prevent SQL injection attacks, which occur when untrusted input, such as user-supplied data, is inserted directly into SQL queries. Prepared Statements treat these inputs as parameters, eliminating the possibility of malicious manipulation.

Performance

Prepared Statements are compiled once by the database and can be reused with different parameters. This reduces the load on the database and improves performance compared to building dynamic queries every run.

Query Optimization

Databases can optimize the execution of Prepared Statements, resulting in a more efficient execution plan. This can lead to performance improvements compared to dynamic SQL queries.

Ease of Use

Using Prepared Statements simplifies the construction of queries, especially when they involve dynamic data values. Parameters are entered safely without the need for complicated string manipulation.

Code Maintenance

Code that uses Prepared Statements tends to be clearer and easier to maintain than code that builds dynamic SQL queries by concatenating strings. This helps with understanding the code and reduces the likelihood of errors.

Example in Java using JDBC:

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class ExamplePreparedStatement {
     public static void main(String[] args) {
         try (Connection connection = getConnection()) {
             String name = "John";
             int age = 25;

             // example of Prepared Statement
             String sql = "INSERT INTO users (name, age) VALUES (?, ?)";
             try (PreparedStatement preparedStatement = connection.prepareStatement(sql)) {
                 preparedStatement.setString(1, name);
                 preparedStatement.setInt(2, age);
                 preparedStatement.executeUpdate();
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }

     // dummy method to obtain a database connection
     private static Connection getConnection() throws SQLException {
         // dummy implementation
         return null;
     }
}

In this example, "?" are placeholders for the parameters. The "setString" and "setInt" method are used to assign values to parameters before executing the query. This is a simple example, but the approach scales to more complex queries.