Menjalankan Kueri SQL Dasar

Melakukan Query ke Basis Data PostgreSQL di Java

Miller Trujillo

Staff Software Engineer

Pernyataan dalam JDBC

Gunakan executeQuery() untuk pernyataan SELECT
Gunakan executeUpdate() untuk INSERT, UPDATE, DELETE

Pernyataan sebagai pengirim pesan

Membuat Pernyataan

String sql = "SELECT book_id, title, publication_year FROM books";

try (Connection conn = DriverManager.getConnection(url, user, password);
     Statement stmt = conn.createStatement();
     ResultSet rs = stmt.executeQuery(sql)) {

Membaca Hasil dengan ResultSet

String sql = "SELECT book_id, title, publication_year FROM books";
try (Connection conn = DriverManager.getConnection(url, user, password);
     Statement stmt = conn.createStatement();
     ResultSet rs = stmt.executeQuery(sql)) {

  while (rs.next()) {

    int id = rs.getInt("book_id");
    String title = rs.getString("title");
    int year = rs.getInt("publication_year");
    System.out.println(id + " | " + title + " (" + year + ")");}}

1 | Effective Java (2018)
2 | Clean Code (2008)
...

Menangani Pengecualian

try {
    Statement stmt = conn.createStatement();

    stmt.executeQuery("SELECT * FROM unknown_table");

} catch (SQLException e) {

    System.err.println("Error: " + e.getMessage());
    System.err.println("SQLState: " + e.getSQLState()); 
}

Error: ERROR: relation "unknown_table" does not exist
  Position: 15
SQLState: 42P01

Ringkasan

Statement mengirim perintah SQL ke database
ResultSet menyimpan hasil kueri, gunakan next() untuk iterasi
Metode getter: getInt(), getString(), getDate()
executeQuery() untuk SELECT, executeUpdate() untuk modifikasi
Tangani kesalahan dengan SQLException

Ringkasan

Ayo berlatih!

Melakukan Query ke Basis Data PostgreSQL di Java