Category: java Mysql

  • Khóa học miễn phí Java & MySQL – Drop Database nhận dự án làm có lương

    Java & MySQL – Drop Database Example



    This chapter provides an example on how to drop an existing Database using JDBC application. Before executing the following example, make sure you have the following in place −

    • To execute the following example you need to replace the username and password with your actual user name and password.

    • Your MySQL is up and running.

    NOTE − This is a serious operation and you have to make a firm decision before proceeding to delete a database because everything you have in your database would be lost.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.

    • Deleting a database does not require database name to be in your database URL. Following example would delete STUDENTS database.

    • Execute a query − Requires using an object of type Statement for building and submitting an SQL statement to delete the database.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/";
       static final String USER = "guest";
       static final String PASS = "guest123";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();
          ) {
             String sql = "DROP DATABASE STUDENTS";
             stmt.executeUpdate(sql);
             System.out.println("Database dropped successfully...");
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Database dropped successfully...
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Select Database nhận dự án làm có lương

    Java & MySQL – Select Database Example



    This chapter provides an example on how to select a Database using JDBC application. Before executing the following example, make sure you have the following in place −

    • To execute the following example you need to replace the username and password with your actual user name and password.

    • Your MySQL database you are using, is up and running.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for the database programming. Most often, using import java.sql.* will suffice.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a selected database.

    • Selection of database is made while you prepare database URL. Following example would make connection with STUDENTS database.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in JDBCExample.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class JDBCExample {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
    
       public static void main(String[] args) {
          System.out.println("Connecting to a selected database...");
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);) {
             System.out.println("Connected database successfully...");
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac JDBCExample.java
    C:>
    

    When you run JDBCExample, it produces the following result −

    C:>java JDBCExample
    Connecting to a selected database...
    Connected database successfully...
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Create Tables nhận dự án làm có lương

    Java & MySQL – Create Table Example



    This chapter provides an example on how to create a table using JDBC application. Before executing the following example, make sure you have the following in place −

    • To execute the following example you can replace the username and password with your actual user name and password.

    • Your MySQL is up and running.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.

    • Execute a query − Requires using an object of type Statement for building and submitting an SQL statement to create a table in a seleted database.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();
          ) {
              String sql = "CREATE TABLE REGISTRATION " +
                       "(id INTEGER not NULL, " +
                       " first VARCHAR(255), " +
                       " last VARCHAR(255), " +
                       " age INTEGER, " +
                       " PRIMARY KEY ( id ))";
    
             stmt.executeUpdate(sql);
             System.out.println("Created table in given database...");
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Created table in given database...
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Drop Tables nhận dự án làm có lương

    Java & MySQL – Drop Table Example



    This chapter provides an example on how to delete a table using JDBC application. Before executing the following example, make sure you have the following in place −

    • To execute the following example you can replace the username and password with your actual user name and password.

    • Your MySQL database you are using, is up and running.

    NOTE − This is a serious operation and you have to make a firm decision before proceeding to delete a table, because everything you have in your table would be lost.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.

    • Execute a query − Requires using an object of type Statement for building and submitting an SQL statement to drop a table in a seleted database.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();
          ) {
             String sql = "DROP TABLE REGISTRATION";
             stmt.executeUpdate(sql);
             System.out.println("Table deleted in given database...");
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Table deleted in given database...
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Insert Records nhận dự án làm có lương

    Java & MySQL – Insert Records Example



    This chapter provides an example on how to insert records in a table using JDBC application. Before executing following example, make sure you have the following in place −

    • To execute the following example you can replace the username and password with your actual user name and password.

    • Your MySQL database you are using is up and running.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.

    • Register the JDBC driver − Requires that you initialize a driver so you can open a communications channel with the database.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.

    • Execute a query − Requires using an object of type Statement for building and submitting an SQL statement to insert records into a table.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();
          ) {
             // Execute a query
             System.out.println("Inserting records into the table...");
             String sql = "INSERT INTO Registration VALUES (100, ''Zara'', ''Ali'', 18)";
             stmt.executeUpdate(sql);
             sql = "INSERT INTO Registration VALUES (101, ''Mahnaz'', ''Fatma'', 25)";
             stmt.executeUpdate(sql);
             sql = "INSERT INTO Registration VALUES (102, ''Zaid'', ''Khan'', 30)";
             stmt.executeUpdate(sql);
             sql = "INSERT INTO Registration VALUES(103, ''Sumit'', ''Mittal'', 28)";
             stmt.executeUpdate(sql);
             System.out.println("Inserted records into the table...");
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Inserting records into the table...
    Inserted records into the table...
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Navigate Result Set nhận dự án làm có lương

    Java & MySQL – Navigating a ResultSet



    There are several methods in the ResultSet interface that involve moving the cursor, including −

    S.N. Methods & Description
    1 public void beforeFirst() throws SQLException

    Moves the cursor just before the first row.

    2 public void afterLast() throws SQLException

    Moves the cursor just after the last row.

    3 public boolean first() throws SQLException

    Moves the cursor to the first row.

    4 public void last() throws SQLException

    Moves the cursor to the last row.

    5 public boolean absolute(int row) throws SQLException

    Moves the cursor to the specified row.

    6 public boolean relative(int row) throws SQLException

    Moves the cursor the given number of rows forward or backward, from where it is currently pointing.

    7 public boolean previous() throws SQLException

    Moves the cursor to the previous row. This method returns false if the previous row is off the result set.

    8 public boolean next() throws SQLException

    Moves the cursor to the next row. This method returns false if there are no more rows in the result set.

    9 public int getRow() throws SQLException

    Returns the row number that the cursor is pointing to.

    10 public void moveToInsertRow() throws SQLException

    Moves the cursor to a special row in the result set that can be used to insert a new row into the database. The current cursor location is remembered.

    11 public void moveToCurrentRow() throws SQLException

    Moves the cursor back to the current row if the cursor is currently at the insert row; otherwise, this method does nothing

    Following is the example which makes use of few navigation methods described.

    This sample code has been written based on the environment and database setup done in the previous chapters.

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
       static final String QUERY = "SELECT id, first, last, age FROM Employees";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement(
             ResultSet.TYPE_SCROLL_INSENSITIVE,
             ResultSet.CONCUR_READ_ONLY);
             ResultSet rs = stmt.executeQuery(QUERY);
          ) {
             // Move cursor to the last row.
             System.out.println("Moving cursor to the last...");
             rs.last();
    
             // Extract data from result set
             System.out.println("Displaying record...");
             //Retrieve by column name
             int id  = rs.getInt("id");
             int age = rs.getInt("age");
             String first = rs.getString("first");
             String last = rs.getString("last");
    
             // Display values
             System.out.print("ID: " + id);
             System.out.print(", Age: " + age);
             System.out.print(", First: " + first);
             System.out.println(", Last: " + last);
    
             // Move cursor to the first row.
             System.out.println("Moving cursor to the first row...");
             rs.first();
    
             // Extract data from result set
             System.out.println("Displaying record...");
             // Retrieve by column name
             id  = rs.getInt("id");
             age = rs.getInt("age");
             first = rs.getString("first");
             last = rs.getString("last");
    
             // Display values
             System.out.print("ID: " + id);
             System.out.print(", Age: " + age);
             System.out.print(", First: " + first);
             System.out.println(", Last: " + last);
             // Move cursor to the first row.
    
             System.out.println("Moving cursor to the next row...");
             rs.next();
    
             // Extract data from result set
             System.out.println("Displaying record...");
             id  = rs.getInt("id");
             age = rs.getInt("age");
             first = rs.getString("first");
             last = rs.getString("last");
    
             // Display values
             System.out.print("ID: " + id);
             System.out.print(", Age: " + age);
             System.out.print(", First: " + first);
             System.out.println(", Last: " + last);
    
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Moving cursor to the last...
    Displaying record...
    ID: 103, Age: 30, First: Sumit, Last: Mittal
    Moving cursor to the first row...
    Displaying record...
    ID: 100, Age: 18, First: Zara, Last: Ali
    Moving cursor to the next row...
    Displaying record...
    ID: 101, Age: 25, First: Mehnaz, Last: Fatma
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Where Clause nhận dự án làm có lương

    Java & MySQL – WHERE Clause Example



    This chapter provides an example on how to select records from a table using JDBC application. This would add additional conditions using WHERE clause while selecting records from the table. Before executing the following example, make sure you have the following in place −

    • To execute the following example you can replace the username and password with your actual user name and password.

    • Your MySQL database you are using, is up and running.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for the database programming. Most often, using import java.sql.* will suffice.

    • Register the JDBC driver − Requires that you initialize a driver so you can open a communications channel with the database.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.

    • Execute a query − Requires using an object of type Statement for building and submitting an SQL statement to fetch records from a table, which meet the given condition. This Query makes use of the WHERE clause to select records.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
       static final String QUERY = "SELECT id, first, last, age FROM Registration";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();) {
             System.out.println("Fetching records without condition...");
             ResultSet rs = stmt.executeQuery(QUERY);
             while(rs.next()){
                //Display values
                System.out.print("ID: " + rs.getInt("id"));
                System.out.print(", Age: " + rs.getInt("age"));
                System.out.print(", First: " + rs.getString("first"));
                System.out.println(", Last: " + rs.getString("last"));
             }
    
             // Select all records having ID equal or greater than 101
             System.out.println("Fetching records with condition...");
             String sql = "SELECT id, first, last, age FROM Registration" +
                " WHERE id >= 101 ";
             rs = stmt.executeQuery(sql);
    
             while(rs.next()){
                //Display values
                System.out.print("ID: " + rs.getInt("id"));
                System.out.print(", Age: " + rs.getInt("age"));
                System.out.print(", First: " + rs.getString("first"));
                System.out.println(", Last: " + rs.getString("last"));
             }
             rs.close();
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Fetching records without condition...
    ID: 100, Age: 30, First: Zara, Last: Ali
    ID: 102, Age: 30, First: Zaid, Last: Khan
    ID: 103, Age: 28, First: Sumit, Last: Mittal
    Fetching records with condition...
    ID: 102, Age: 30, First: Zaid, Last: Khan
    ID: 103, Age: 28, First: Sumit, Last: Mittal
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Update Result Set nhận dự án làm có lương

    Java & MySQL – Updating a ResultSet



    The ResultSet interface contains a collection of update methods for updating the data of a result set.

    As with the get methods, there are two update methods for each data type −

    • One that takes in a column name.

    • One that takes in a column index.

    For example, to update a String column of the current row of a result set, you would use one of the following updateString() methods −

    S.N. Methods & Description
    1 public void updateString(int columnIndex, String s) throws SQLException

    Changes the String in the specified column to the value of s.

    2 public void updateString(String columnName, String s) throws SQLException

    Similar to the previous method, except that the column is specified by its name instead of its index.

    There are update methods for the eight primitive data types, as well as String, Object, URL, and the SQL data types in the java.sql package.

    Updating a row in the result set changes the columns of the current row in the ResultSet object, but not in the underlying database. To update your changes to the row in the database, you need to invoke one of the following methods.

    S.N. Methods & Description
    1 public void updateRow()

    Updates the current row by updating the corresponding row in the database.

    2 public void deleteRow()

    Deletes the current row from the database

    3 public void refreshRow()

    Refreshes the data in the result set to reflect any recent changes in the database.

    4 public void cancelRowUpdates()

    Cancels any updates made on the current row.

    5 public void insertRow()

    Inserts a row into the database. This method can only be invoked when the cursor is pointing to the insert row.

    Following is the example, which makes use of the ResultSet.CONCUR_UPDATABLE and ResultSet.TYPE_SCROLL_INSENSITIVE described in the Result Set tutorial. This example would explain INSERT, UPDATE and DELETE operation on a table.

    It should be noted that tables you are working on should have Primary Key set properly. Let”s update our referece table first.

    Drop the table and Create the table Employees again as follows −

    mysql> use TUTORIALSPOINT;
    mysql> drop table Employees;
    Query OK, 0 rows affected (0.08 sec)
    mysql> create table Employees
        -> (
        -> id int primary key auto_increment,
        -> age int not null,
        -> first varchar (255),
        -> last varchar (255)
        -> );
    Query OK, 0 rows affected (0.08 sec)
    mysql>
    

    Create Data Records

    Finally you create few records in Employee table as follows −

    mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (18, ''Zara'', ''Ali'');
    Query OK, 1 row affected (0.05 sec)
    
    mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (25, ''Mahnaz'', ''Fatma'');
    Query OK, 1 row affected (0.00 sec)
    
    mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (30, ''Zaid'', ''Khan'');
    Query OK, 1 row affected (0.00 sec)
    
    mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (28, ''Sumit'', ''Mittal'');
    Query OK, 1 row affected (0.00 sec)
    
    mysql>
    

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
       static final String QUERY = "SELECT id, first, last, age FROM Employees";
    
       public static void printResultSet(ResultSet rs) throws SQLException{
          // Ensure we start with first row
          rs.beforeFirst();
          while(rs.next()){
             // Display values
             System.out.print("ID: " + rs.getInt("id"));
             System.out.print(", Age: " + rs.getInt("age"));
             System.out.print(", First: " + rs.getString("first"));
             System.out.println(", Last: " + rs.getString("last"));
          }
          System.out.println();
       }
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement(
             ResultSet.TYPE_SCROLL_INSENSITIVE,
             ResultSet.CONCUR_UPDATABLE);
             ResultSet rs = stmt.executeQuery(QUERY);
          ) {
    
             System.out.println("List result set for reference....");
             printResultSet(rs);
    
             // Loop through result set and add 5 in age
             // Move to Before first position so while-loop works properly
             rs.beforeFirst();
             //STEP 7: Extract data from result set
             while(rs.next()){
                // Retrieve by column name
                int newAge = rs.getInt("age") + 5;
                rs.updateDouble( "age", newAge );
                rs.updateRow();
             }
             System.out.println("List result set showing new ages...");
             printResultSet(rs);
    
             // Insert a record into the table.
             // Move to insert row and add column data with updateXXX()
             System.out.println("Inserting a new record...");
             rs.moveToInsertRow();
             rs.updateString("first","John");
             rs.updateString("last","Paul");
             rs.updateInt("age",40);
             // Commit row
             rs.insertRow();
    
             System.out.println("List result set showing new set...");
             printResultSet(rs);
    
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    List result set for reference....
    ID: 1, Age: 18, First: Zara, Last: Ali
    ID: 2, Age: 25, First: Mahnaz, Last: Fatma
    ID: 3, Age: 30, First: Zaid, Last: Khan
    ID: 4, Age: 28, First: Sumit, Last: Mittal
    
    List result set showing new ages...
    ID: 1, Age: 23, First: Zara, Last: Ali
    ID: 2, Age: 30, First: Mahnaz, Last: Fatma
    ID: 3, Age: 35, First: Zaid, Last: Khan
    ID: 4, Age: 33, First: Sumit, Last: Mittal
    
    Inserting a new record...
    List result set showing new set...
    ID: 1, Age: 23, First: Zara, Last: Ali
    ID: 2, Age: 30, First: Mahnaz, Last: Fatma
    ID: 3, Age: 35, First: Zaid, Last: Khan
    ID: 4, Age: 33, First: Sumit, Last: Mittal
    ID: 5, Age: 40, First: John, Last: Paul
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – Select Records nhận dự án làm có lương

    Java & MySQL – Select Records Example



    This chapter provides an example on how to select/ fetch records from a table using JDBC application. Before executing the following example, make sure you have the following in place −

    • To execute the following example you can replace the username and password with your actual user name and password.

    • Your MySQL database you are using is up and running.

    Required Steps

    The following steps are required to create a new Database using JDBC application −

    • Import the packages − Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.

    • Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.

    • Execute a query − Requires using an object of type Statement for building and submitting an SQL statement to select (i.e. fetch ) records from a table.

    • Extract Data − Once SQL query is executed, you can fetch records from the table.

    • Clean up the environment − try with resources automatically closes the resources.

    Sample Code

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
       static final String QUERY = "SELECT id, first, last, age FROM Registration";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery(QUERY);
          ) {
             while(rs.next()){
                //Display values
                System.out.print("ID: " + rs.getInt("id"));
                System.out.print(", Age: " + rs.getInt("age"));
                System.out.print(", First: " + rs.getString("first"));
                System.out.println(", Last: " + rs.getString("last"));
             }
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    ID: 100, Age: 18, First: Zara, Last: Ali
    ID: 101, Age: 25, First: Mahnaz, Last: Fatma
    ID: 102, Age: 30, First: Zaid, Last: Khan
    ID: 103, Age: 28, First: Sumit, Last: Mittal
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

  • Khóa học miễn phí Java & MySQL – View Result Set nhận dự án làm có lương

    Java & MySQL – Viewing a ResultSet



    The ResultSet interface contains dozens of methods for getting the data of the current row.

    There is a get method for each of the possible data types, and each get method has two versions −

    • One that takes in a column name.

    • One that takes in a column index.

    For example, if the column you are interested in viewing contains an int, you need to use one of the getInt() methods of ResultSet −

    S.N. Methods & Description
    1 public int getInt(String columnName) throws SQLException

    Returns the int in the current row in the column named columnName.

    2 public int getInt(int columnIndex) throws SQLException

    Returns the int in the current row in the specified column index. The column index starts at 1, meaning the first column of a row is 1, the second column of a row is 2, and so on.

    Similarly, there are get methods in the ResultSet interface for each of the eight Java primitive types, as well as common types such as java.lang.String, java.lang.Object, and java.net.URL.

    There are also methods for getting SQL data types java.sql.Date, java.sql.Time, java.sql.TimeStamp, java.sql.Clob, and java.sql.Blob. Check the documentation for more information about using these SQL data types.

    Following is the example which makes use of few viewing methods described.

    This sample code has been written based on the environment and database setup done in the previous chapters.

    Copy and paste the following example in TestApplication.java, compile and run as follows −

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class TestApplication {
       static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
       static final String USER = "guest";
       static final String PASS = "guest123";
       static final String QUERY = "SELECT id, first, last, age FROM Employees";
    
       public static void main(String[] args) {
          // Open a connection
          try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement(
             ResultSet.TYPE_SCROLL_INSENSITIVE,
             ResultSet.CONCUR_READ_ONLY);
             ResultSet rs = stmt.executeQuery(QUERY);
          ) {
             // Move cursor to the last row.
             System.out.println("Moving cursor to the last...");
             rs.last();
    
             // Extract data from result set
             System.out.println("Displaying record...");
             //Retrieve by column name
             int id  = rs.getInt("id");
             int age = rs.getInt("age");
             String first = rs.getString("first");
             String last = rs.getString("last");
    
             // Display values
             System.out.print("ID: " + id);
             System.out.print(", Age: " + age);
             System.out.print(", First: " + first);
             System.out.println(", Last: " + last);
    
             // Move cursor to the first row.
             System.out.println("Moving cursor to the first row...");
             rs.first();
    
             // Extract data from result set
             System.out.println("Displaying record...");
             // Retrieve by column name
             id  = rs.getInt("id");
             age = rs.getInt("age");
             first = rs.getString("first");
             last = rs.getString("last");
    
             // Display values
             System.out.print("ID: " + id);
             System.out.print(", Age: " + age);
             System.out.print(", First: " + first);
             System.out.println(", Last: " + last);
             // Move cursor to the first row.
    
             System.out.println("Moving cursor to the next row...");
             rs.next();
    
             // Extract data from result set
             System.out.println("Displaying record...");
             id  = rs.getInt("id");
             age = rs.getInt("age");
             first = rs.getString("first");
             last = rs.getString("last");
    
             // Display values
             System.out.print("ID: " + id);
             System.out.print(", Age: " + age);
             System.out.print(", First: " + first);
             System.out.println(", Last: " + last);
    
          } catch (SQLException e) {
             e.printStackTrace();
          }
       }
    }
    

    Now let us compile the above example as follows −

    C:>javac TestApplication.java
    C:>
    

    When you run TestApplication, it produces the following result −

    C:>java TestApplication
    Moving cursor to the last...
    Displaying record...
    ID: 103, Age: 30, First: Sumit, Last: Mittal
    Moving cursor to the first row...
    Displaying record...
    ID: 100, Age: 18, First: Zara, Last: Ali
    Moving cursor to the next row...
    Displaying record...
    ID: 101, Age: 25, First: Mehnaz, Last: Fatma
    C:>
    

    Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc