Database and JDBC

This lesson introduces databases, SQL, and Java Database Connectivity (JDBC). It covers creating databases and tables, connecting Java programs to a database, and performing basic CRUD operations.

A database is an organized collection of data stored so it can be searched, updated, and managed efficiently. A database management system (DBMS) controls access to the database.

Many relational databases use SQL, which stands for Structured Query Language.

JDBC stands for Java Database Connectivity. It is a Java API that allows Java programs to connect to databases, run SQL statements, and process results.

Common JDBC tasks include:

1. Connect to a database.
2. Create a SQL statement or prepared statement.
3. Execute a query or update.
4. Read returned records.
5. Insert, update, or delete data.
6. Close database resources.

A typical JDBC program follows this structure:

Connection connection = DriverManager.getConnection(url, user, password);
Statement statement = connection.createStatement();
ResultSet result = statement.executeQuery("SELECT * FROM students");

Important JDBC classes and interfaces:

SQL statements are used to create and manage data.

Common SQL commands:

The exact connection string depends on the database and driver being used. For MySQL, the connection string usually follows this pattern:

jdbc:mysql://localhost:3306/database_name

Before running a JDBC program, make sure the database server is running and the correct JDBC driver is included in the project.

For user input, prefer PreparedStatement instead of building SQL by concatenating strings. Prepared statements reduce errors and help prevent SQL injection.

Always close database resources. The examples above use try-with-resources, which closes resources automatically.

A real JDBC connection needs a running database server. This example walks through the steps and simulates the output you would get.