[JAVA] JDBC promises and examples of how to write

JDBC is a Java API that can perform database processing (SQL statements). There are java.sql (core: J2SE), javax.sql (standard extension: J2EE) and so on.

Below is an example using java.sql.

An example of executing a SQL statement in a fixed manner and displaying the result

import java.sql.*;

public class class name{
   public static void main(String args[])
      throws SQLException, ClassNotFoundException { //Exception handling For displaying error pages

      String drv = "oracle.jdbc.OracleDriver"; // Oracle JDBC (Type4)Specify
      String url = "jdbc:oracle:thin:@localhost:1521:Database name"; //Database url

      Class.forName(drv); //Load the driver
      Connection con =  DriverManager.getConnection(url,User name,password); //Connect to database


      Statement stmt = con.createStatement(); //Preparing for inquiries
      String qry = "SQL statement for example SELECT*FROM table name"; //Query preparation
      ResultSet rs = stmt.executeQuery(qry); //Execute SQL statement and receive result as ResultSet


      //ResltSet data income line by line
      while(rs.next()){ // next()Specify each row in the method and return false when the table is finished.
String Column name 1= rs.getString("Column name 1");
Int column name 2= rs.getInt("Column name");
         System.out.println(Column name 1+ "\t" +Column name 2); //display
      }

      //Close connection with database
      rs.close();
      stmt.close();
      con.close();
   }
}

Example of receiving input and executing SQL

If you want to receive input and insert it into SQL statement, the notation such as preparation of SQL statement changes.

import java.sql.*;

public class class name{
   public static void main(String args[])
      throws SQLException, ClassNotFoundException { //Exception handling For displaying error pages

      String drv = "oracle.jdbc.OracleDriver"; // Oracle JDBC (Type4)Specify
      String url = "jdbc:oracle:thin:@localhost:1521:Database name"; //Database url

      Class.forName(drv); //Load the driver
      Connection con =  DriverManager.getConnection(url,User name,password); //Connect to database


      String qry = "SQL statement for example SELECT*FROM table name where column name= ?AND column name= ?";
                               // ?The input value is inserted in the part of. 1 from the left,Specify with 2 and a number.
      PreparedStatement ps = con.prepareStatement(qry); //Preparing for inquiries
      ps.setString(1,Input 1); //1st?Insert input into. If the input is a string.
      ps.setInt(2,Input 2); //Second?Insert input into. If the input is an integer type.
      ResultSet rs = ps.executeQuery(); //Execute SQL statement and receive result as ResultSet


      //ResltSet data income line by line
      while(rs.next()){ // next()Specify each row in the method and return false when the table is finished.
String Column name 1= rs.getString("Column name 1");
Int column name 2= rs.getInt("Column name");
         System.out.println(Column name 1+ "\t" +Column name 2); //display
      }

      //Close connection with database
      rs.close();
      ps.close();
      con.close();
   }
}