CRUD Operations using JDBC

INSERT INTO table VALUES(...);
SELECT * FROM table;
UPDATE table SET column=? WHERE id=?;
DELETE FROM table WHERE id=?;

import java.sql.*;

public class Main {

  public static void main(String[] args) {

    try {

      Connection con = DriverManager.getConnection(
        "jdbc:mysql://localhost:3306/college",
        "root",
        "password"
      );

      // CREATE (INSERT)
      String insertQuery = "INSERT INTO students(name, age) VALUES('John', 22)";
      Statement stmt = con.createStatement();
      stmt.executeUpdate(insertQuery);

      // READ (SELECT)
      String selectQuery = "SELECT * FROM students";
      ResultSet rs = stmt.executeQuery(selectQuery);

      while (rs.next()) {
        System.out.println(rs.getInt("id") + " " + rs.getString("name"));
      }

      // UPDATE
      String updateQuery = "UPDATE students SET name='Alex' WHERE id=1";
      stmt.executeUpdate(updateQuery);

      // DELETE
      String deleteQuery = "DELETE FROM students WHERE id=2";
      stmt.executeUpdate(deleteQuery);

      con.close();

    } catch (Exception e) {
      e.printStackTrace();
    }

  }
}

// Output:
// Data inserted, displayed, updated, and deleted successfully

• 1 Create – Insert data into database.
• 2 Read – Retrieve data from database.
• 3 Update – Modify existing data.
• 4 Delete – Remove data from database.

• 1 Establish database connection.
• 2 Create SQL query.
• 3 Execute query using Statement.
• 4 Process results if needed.
• 5 Close connection.

• 1 executeUpdate() – for INSERT, UPDATE, DELETE.
• 2 executeQuery() – for SELECT.
• 3 execute() – for general use.
• 4 PreparedStatement – safer execution.

• 1 Core operations of any application.
• 2 Used in all database systems.
• 3 Essential for backend development.
• 4 Forms the base of data handling.

• 1 Used in HRMS systems for employee management.
• 2 Used in banking systems for account transactions.
• 3 Used in inventory management systems.
• 4 Used in ERP applications.
• 5 SaaS products use CRUD Operations using JDBC in services, dashboards, background jobs, and API workflows.
• 6 ERP and banking systems apply CRUD Operations using JDBC with validation, logging, review, and rollback plans.
• 7 E-commerce and healthcare platforms use CRUD Operations using JDBC carefully because reliability and data correctness matter.

• 1 A Java program first evaluates the surrounding context, then applies the CRUD Operations using JDBC rules to the current data.
• 2 The important mental model is input, transformation, result, and failure path.
• 3 In production, the same flow usually sits inside a larger layer such as a controller, service, repository, job, or UI component.

• 1 Choose the simplest implementation first, then measure real workloads.
• 2 Watch for repeated work inside loops, unnecessary allocations, and slow I/O in hot paths.
• 3 Prefer clear data structures and stable APIs before micro-optimizing syntax.

• 1 Treat external input as untrusted until it is validated.
• 2 Avoid hardcoded secrets and never print sensitive values in examples or logs.
• 3 Use established libraries for authentication, encryption, parsing, and database access.

• 1 Using raw Statement instead of PreparedStatement.
• 2 Not handling SQL exceptions.
• 3 Forgetting to close connection.
• 4 Writing SQL queries directly in code.
• 5 Skipping the small working example before adding framework code.
• 6 Ignoring null, empty, duplicate, and boundary inputs.
• 7 Mixing business logic, input handling, and output formatting in one place.
• 8 Using broad error handling that hides the real failure.
• 9 Forgetting to test the behavior after refactoring.
• 10 Adding clever code that future maintainers will struggle to read.

• 1 Use PreparedStatement for security.
• 2 Close all JDBC resources properly.
• 3 Separate SQL logic from business logic.
• 4 Use connection pooling in production.
• 5 Start with clear requirements and one minimal working example.
• 6 Use meaningful names that explain business intent.
• 7 Keep examples small enough to debug line by line.
• 8 Validate input at every trust boundary.
• 9 Handle errors explicitly and preserve useful context.
• 10 Prefer simple control flow over deeply nested logic.
• 11 Separate domain logic from I/O and framework code.
• 12 Write tests for normal, boundary, and failure cases.
• 13 Review security assumptions before production use.
• 14 Measure performance before optimizing.
• 15 Document non-obvious decisions close to the code or in project notes.
• 16 Use official documentation when behavior is version-specific.
• 17 Keep dependencies current and remove unused code.
• 18 Avoid hardcoded secrets, credentials, and environment-specific paths.
• 19 Log operational events without exposing sensitive data.
• 20 Design examples so learners can safely modify and rerun them.

• 1 Beginner: rewrite the example with different names and values.
• 2 Intermediate: add validation and handle one expected failure case.
• 3 Advanced: place CRUD Operations using JDBC inside a small service-style design with tests.

• 1 Build a small Java console feature that demonstrates CRUD Operations using JDBC.
• 2 Accept input, process it with the concept, print a clear result, and handle invalid input.
• 3 Add a README note explaining the design choice and two edge cases you tested.

• 1 If the program does not compile, check spelling, imports, braces, and file/class names first.
• 2 If output is unexpected, print intermediate values and verify each branch of the logic.
• 3 If the design feels complex, reduce it to the smallest working example and add pieces back one at a time.

• 1 Practice CRUD Operations using JDBC with a second example from a business domain such as inventory, payroll, banking, or e-commerce.
• 2 Review related Java topics that cover data flow, error handling, testing, and clean design.
• 3 Compare your solution with official documentation and simplify anything you cannot explain clearly.