MariaDB haladó

• Szerző: Sallai András
• Copyright © 2020, Sallai András
• Szerkesztve: 2020, 2023
• Licenc: CC BY-SA 4.0
• Web: https://szit.hu

Ha több SQL utasításunk van, amit futtatni kell, az addBatch() metódussal felvehetjük őket, majd az executeBatch() metódussal egyszerre futtatjuk őket, egymás után.

Statement stmt = c.createStatement();
String sql1 = "create database vmi1";
String sql2 = "create database vmi2";  
String sql3 = "create database vmi3";  
stmt.addBatch(sql1);
stmt.addBatch(sql2);     
stmt.addBatch(sql3);     
stmt.executeBatch();

if (conn != null) {
    DatabaseMetaData meta = conn.getMetaData();
    System.out.println("Driver név: " + meta.getDriverName());                
}

Használható metódusok:

• getCatalogSeparator()
• getCatalogTerm()
• getDatabaseProductName()
• getDatabaseProductVersion()
• getDriverName()
• getDriverVersion()
• getExtraNameCharacters()
• getIdentifierQuoteString()
• getNumericFunctions()
• getProcedureTerm()
• getSQLKeywords()
• getSchemaTerm()
• getSearchStringEscape()
• getStringFunctions()
• getSystemFunctions()
• getTimeDateFunctions()
• getURL()
• getUserName()

String sql = "insert into tabla1 (name) values(?)";
 
PreparedStatement pstmt = conn.prepareStatement(sql,
        Statement.RETURN_GENERATED_KEYS);
 
pstmt.setString(1, "János")
pstmt.execute();
 
ResultSet rs = pstmt.getGeneratedKeys();
int genKey = 0;
if (rs.next()) {
    genKey = rs.getInt(1);
}
 
System.out.println("az: " + genKey);

import java.util.logging.Level;  
import java.util.logging.Logger; 
 
//...
 
try {
    //...
}catch(SQLException ex) {
    Logger.getLogger(Mariadb.class.getName()).log(Level.SEVERE, null, ex);
}

A „Mariadb” az az osztály, amelyben a kapcsolatot létrehozzuk.

A MariaDB driver ellenőrzése:

Class.forName("org.mariadb.jdbc.Driver");

App.java

import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.DriverManager;
import java.util.ArrayList;
 
class App {
    public static ArrayList<Employee> getEmployees() {
        ArrayList<Employee> employeeList = new ArrayList<>();
        Connection conn = null;
        try {
            Class.forName("org.mariadb.jdbc.Driver");
            String url = "jdbc:mariadb://localhost:3306/surubt";
            conn = DriverManager.getConnection(url, 
            "surubt", "titok");
 
            String sql = "select * from employees";        
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery(sql);
            while(rs.next()) {
                Employee emp = new Employee(
                    rs.getInt("id"),
                    rs.getString("name"),
                    rs.getString("city"),
                    rs.getDouble("salary"),
                    rs.getDate("birth").toLocalDate()
                    );
                employeeList.add(emp);
            }
 
 
        }catch(SQLException ex) {
            System.err.println("Hiba! Az SQL művelet sikertelen!");
            System.err.println(ex.getMessage());
        }catch(ClassNotFoundException ex) {
            System.err.println("Hiba! A MariaDB driver nem található!");
            System.err.println(ex.getMessage());            
        }
        return employeeList;
    }
 
    public static void main(String[] args) {
        ArrayList<Employee> employeeList;
        employeeList = getEmployees();
        employeeList.forEach(emp -> {
            System.out.println(emp.name);
        });
    }
}