What are prepared statements in Java
💡 Concept: PreparedStatement
A PreparedStatement in JDBC is a precompiled SQL statement that can be executed multiple times with different parameters, enhancing both performance and security.
📘 Quick Intro
Prepared statements are used to safely execute parameterized SQL queries in Java. They help avoid SQL injection and reduce the overhead of repeatedly parsing SQL syntax.
🧠 Analogy
Think of a prepared statement like a reusable baking mold. You create the mold once (prepare the SQL), and reuse it with different ingredients (parameters) to bake cakes (queries) efficiently and consistently.
🔧 Technical Explanation
PreparedStatementis a subinterface ofStatement.- It allows SQL statements with placeholders (?) for parameters.
- The SQL is precompiled, which improves execution speed on repeated use.
- It automatically escapes parameter values, preventing SQL injection.
- Parameters are set using methods like
setString(),setInt(), etc.
🎯 Use Cases
- ✅ Repeated execution of the same query with different values
- ✅ Preventing SQL injection in user-driven forms
- ✅ Bulk insertions and batch operations
💻 Example: Using PreparedStatement
import java.sql.*;
public class PreparedStatementExample {
public static void main(String[] args) {
String url = "jdbc:mysql://localhost:3306/testdb";
String user = "root";
String password = "root123";
try (Connection conn = DriverManager.getConnection(url, user, password)) {
String sql = "SELECT * FROM users WHERE username = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "johndoe");
ResultSet rs = pstmt.executeQuery();
while (rs.next()) {
System.out.println(rs.getString("email"));
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
❓ Interview Q&A
Q1: What is a prepared statement in JDBC?
A: A precompiled SQL statement with parameters.
Q2: How does it prevent SQL injection?
A: By separating SQL logic from data inputs.
Q3: Is PreparedStatement reusable?
A: Yes, with different parameter values.
Q4: Which interface does it implement?
A: Statement.
Q5: Can we use it for INSERT and DELETE?
A: Yes.
Q6: What method sets parameters?
A: Methods like setString(), setInt(), etc.
Q7: Can you use multiple ? placeholders?
A: Yes, and set each in order.
Q8: Can PreparedStatement be batched?
A: Yes, using addBatch().
Q9: Is performance better than Statement?
A: Yes, for repeated queries.
Q10: Is SQL precompiled in PreparedStatement?
A: Yes.
📝 MCQs
Q1. Which interface is PreparedStatement a subtype of?
- Driver
- Statement
- Connection
- Query
Q2. Which method sets a string parameter?
- assign()
- setText()
- setString()
- setValue()
Q3. What symbol is used as placeholder in SQL?
- #
- $
- ?
- %
Q4. Why is PreparedStatement safer than Statement?
- Uses more RAM
- Larger buffer
- Prevents SQL injection
- Faster logs
Q5. Is PreparedStatement SQL precompiled?
- No
- Yes
- Sometimes
- Only in MySQL
Q6. Which method executes SELECT?
- run()
- execute()
- executeQuery()
- fetch()
Q7. What method executes INSERT/UPDATE?
- executeQuery()
- executeUpdate()
- runQuery()
- submit()
Q8. Can PreparedStatement improve performance?
- No
- Yes
- Rarely
- Only in JDBC 4.0+
Q9. Is parameter indexing zero-based?
- Yes
- No, starts at 1
- Depends
- Index-free
Q10. Can PreparedStatement be reused with new values?
- No
- Yes
- Sometimes
- Only for SELECT
💡 Bonus Insight
PreparedStatements can be combined with batch processing for large-scale operations, reducing round-trips to the database and increasing throughput.
📄 PDF Download
Need a handy summary for your notes? Download this topic as a PDF!