How do I set the query timeout limit?

The Statement.setQueryTimeout() method set the limit in seconds for query execution time. The execution has no timeout limit when the value is set to zero.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.SQLException;
import java.sql.DriverManager;

public class QueryTimeout {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            Statement stmt = connection.createStatement();

            // Sets the number of seconds the driver will wait for
            // a statement object to execute to the given number of
            // seconds. If the limit is exceeded, an SQLException
            // is thrown.
            stmt.setQueryTimeout(60);

            // Execute sql query
            ResultSet rs = stmt.executeQuery("select * from product");

            while (rs.next()) {
                System.out.println("code: " + rs.getString("code") + 
                                   ", product: " + rs.getString("name") + 
                                   ", price: " + rs.getDouble("price"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I set the fetch size of a statement?

Fetch size is the number of rows that should be fetched from the database on a single database network trip. When more rows are needed, another request is sent by the application to the database server.

Setting the correct fetch size will help our program to perform better by reducing the network communication generated between the program and the database server.

package org.kodejava.jdbc;

import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class SetFetchSizeExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            Statement statement = connection.createStatement();

            // Set the fetch size to 100.
            statement.setFetchSize(100);

            // Execute the given sql query
            String q = "select id, code, name, price from product";
            ResultSet rs = statement.executeQuery(q);

            while (rs.next()) {
                System.out.println("id:" + rs.getLong("id") +
                                   ", code:" + rs.getString("code") +
                                   ", name:" + rs.getString("name") +
                                   ", price:" + rs.getString("price"));
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Example result of the code snippet above is:

id:1, code:P0000001, name:UML Distilled 3rd Edition, price:25.00
id:3, code:P0000003, name:PHP Programming, price:20.00
id:4, code:P0000004, name:Longman Active Study Dictionary, price:40.00
id:5, code:P0000005, name:Ruby on Rails, price:24.00
id:6, code:P0000006, name:Championship Manager, price:0.00
id:7, code:P0000007, name:Transport Tycoon Deluxe, price:0.00
id:8, code:P0000008, name:Roller Coaster Tycoon 3, price:0.00
id:9, code:P0000009, name:Pro Evolution Soccer, price:0.00
id:10, code:P0000010, name:Data Structures, Algorithms, price:50.99

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I set the maximum rows to read in a query?

If you want to limit the result of your query, you can call the Statement.setMaxRows(int max) method. This call will allow the ResultSet object contains a maximum number of records specified in the parameter of the setMaxRows method.

Another way to limit the number of data returned in a query is to use the database-specific command such as the MySQL limit command.

package org.kodejava.jdbc;

import java.sql.*;

public class SetMaxRowExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            Statement statement = connection.createStatement();

            // Executes an SQL query to get the total number of data
            // in product table.
            String query = "select count(*) from product";
            ResultSet rs = statement.executeQuery(query);

            while (rs.next()) {
                System.out.println("Total Products: " + rs.getInt(1));
            }

            // Set the maximum row of data that can be stored in the
            // ResultSet.
            statement.setMaxRows(5);

            // Executes an SQL query to retrieve data from product
            // table.
            query = "select id, code, name, price from product";
            rs = statement.executeQuery(query);

            System.out.println("Data read after the MaxRows is set.");
            while (rs.next()) {
                System.out.println("ID: " + rs.getInt("id")
                                   + ", CODE: " + rs.getString("code")
                                   + ", NAME: " + rs.getString("name")
                                   + ", PRICE: " + rs.getBigDecimal("price"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

When running the code, we’ll see that only 5 records were read from the product table instead of 10 records. This is the result of setting the maximum rows in the Statement object.

Below is the output of our code.

Total Products: 9
Data read after the MaxRows is set.
ID: 1, CODE: P0000001, NAME: UML Distilled 3rd Edition, PRICE: 25.00
ID: 3, CODE: P0000003, NAME: PHP Programming, PRICE: 20.00
ID: 4, CODE: P0000004, NAME: Longman Active Study Dictionary, PRICE: 40.00
ID: 5, CODE: P0000005, NAME: Ruby on Rails, PRICE: 24.00
ID: 6, CODE: P0000006, NAME: Championship Manager, PRICE: 0.00

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I use enum in switch statement?

This example show you how to use enumeration or enum type in a switch statement.

package org.kodejava.basic;

public enum RainbowColor {
    RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET
}
package org.kodejava.basic;

public class EnumSwitch {
    public static void main(String[] args) {
        RainbowColor color = RainbowColor.INDIGO;

        EnumSwitch es = new EnumSwitch();
        String colorCode = es.getColorCode(color);
        System.out.println("ColorCode = #" + colorCode);
    }

    public String getColorCode(RainbowColor color) {
        String colorCode = "";

        // We use the switch-case statement to get the hex color code of our
        // enum type rainbow colors. We can pass the enum type as expression
        // in the switch. In the case statement we only use the enum named
        // constant excluding its type name.
        switch (color) {
            // We use RED instead of RainbowColor.RED
            case RED -> colorCode = "FF0000";
            case ORANGE -> colorCode = "FFA500";
            case YELLOW -> colorCode = "FFFF00";
            case GREEN -> colorCode = "008000";
            case BLUE -> colorCode = "0000FF";
            case INDIGO -> colorCode = "4B0082";
            case VIOLET -> colorCode = "EE82EE";
        }
        return colorCode;
    }
}

How do I make updates in updatable ResultSet?

Using an updatable result set enables our program to update record in the database from the ResultSet object. The operation on the ResultSet object can be updated, inserted or deleted. With this mechanism, we can update a database without executing a query.

In the example below we have a product table with the id, code, name, and price columns. In the first step after we load the result set, we update the product name of the first record. Then we move to the next record and delete it. At last, we insert a new record to a database.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class UpdatableResultSetDemo {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Create an updatable result set. It means that instead of
            // using a separate sql command to update the data, we can
            // update it directly in the result set object.
            //
            // What makes it updatable is because, when creating the
            // statement, we ask the connection object to create a statement
            // with CONCUR_UPDATABLE. The updatable doesn't need to be
            // TYPE_SCROLL_SENSITIVE, but adding this parameter to the
            // statement enables us to go back and forth to update the data.
            Statement statement = connection.createStatement(
                    ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);

            String query = "SELECT id, code, name, price FROM product";
            ResultSet rs = statement.executeQuery(query);

            System.out.println("id\tcode\tname\tprice");

            while (rs.next()) {
                System.out.println(rs.getLong("id") + "\t"
                                   + rs.getString("code") + "\t"
                                   + rs.getString("name") + "\t"
                                   + rs.getDouble("price"));
            }

            // Move to the first row and update the result set data. After
            // we update the row value, we call the updateRow() method to
            // update the data in the database.
            rs.first();
            rs.updateString("name", "UML Distilled 3rd Edition");
            rs.updateRow();

            // Move to the next result set row and delete the row in the
            // result set and apply it to the database.
            rs.next();
            rs.deleteRow();

            // Insert a new row in the result set object with the
            // moveToInsertRow() method. Supply the information to be
            // inserted and finally call the insertRow() method to insert
            // record to the database.
            rs.moveToInsertRow();
            rs.updateString("code", "P0000010");
            rs.updateString("name", "Data Structures, Algorithms");
            rs.updateDouble("price", 50.99);
            rs.insertRow();

            rs.beforeFirst();
            System.out.println();
            System.out.println("id\tcode\tname\tprice");

            while (rs.next()) {
                System.out.println(rs.getLong("id") + "\t"
                                   + rs.getString("code") + "\t"
                                   + rs.getString("name") + "\t"
                                   + rs.getDouble("price"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

The code snippet prints out the following output:

id  code    name    price
1   P0000001    Java 2 Notebook 25.0
2   P0000002    Java Servlet Programming    30.0
3   P0000003    PHP Programming 20.0
4   P0000004    Longman Active Study Dictionary 40.0
5   P0000005    Ruby on Rails   24.0
6   P0000006    Championship Manager    0.0
7   P0000007    Transport Tycoon Deluxe 0.0
8   P0000008    Roller Coaster Tycoon 3 0.0
9   P0000009    Pro Evolution Soccer    0.0

id  code    name    price
1   P0000001    UML Distilled 3rd Edition   25.0
3   P0000003    PHP Programming 20.0
4   P0000004    Longman Active Study Dictionary 40.0
5   P0000005    Ruby on Rails   24.0
6   P0000006    Championship Manager    0.0
7   P0000007    Transport Tycoon Deluxe 0.0
8   P0000008    Roller Coaster Tycoon 3 0.0
9   P0000009    Pro Evolution Soccer    0.0
10  P0000010    Data Structures, Algorithms 50.99

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I create a batch update in JDBC?

A batch statement can be used to execute multiple update commands as single unit in a database manipulation. This statement in the database is not executed one by one but as a single execution instead. In some cases, using a batch update can be more efficient than to execute the commands separately.

In this example, you are shown how to create a batch command to insert some products into a database table.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Arrays;

public class JDBCBatchExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Turn of the auto-commit mode
            connection.setAutoCommit(false);

            try (Statement statement = connection.createStatement()) {
                // And some batch to insert some product information into
                // the product table
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000006', 'Championship Manager')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000007', 'Transport Tycoon Deluxe')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000008', 'Roller Coaster Tycoon 3')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000009', 'Pro Evolution Soccer')");

                // To execute a batch command, we must call the executeBatch()
                // method.
                int[] updateCounts = statement.executeBatch();
                System.out.println("updateCounts = " + Arrays.toString(updateCounts));

                // Commit our transaction
                connection.commit();
            } catch (SQLException e) {
                connection.rollback();
                e.printStackTrace();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I drop table from a database?

This example is to show you how to delete or drop a table from your database. Basically we just send a DROP TABLE command and specify the table name to be deleted to the database. The example below show you how to do it in MySQL database.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class DropTableExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // To delete a table from database we use the DROP TABLE
            // command and specify the table name to be dropped
            String sql = "DROP TABLE IF EXISTS book";

            // Create a statement
            Statement statement = connection.createStatement();
            // Execute the statement to delete the table
            statement.execute(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I create a table in a database?

In this example you can see how to create a table in MySQL database. We create a table called book with the following fields, id, isbn, title, published_year and price. We start by creating a connection to the database and execute the create table query.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class CreateTableExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            String sql = """
                    CREATE TABLE book
                    (
                        id             bigint(20) unsigned NOT NULL AUTO_INCREMENT,
                        isbn           varchar(50)         NOT NULL,
                        title          varchar(100)        NOT NULL,
                        published_year int(11)                      DEFAULT NULL,
                        price          decimal(10, 2)      NOT NULL DEFAULT '0.00',
                        PRIMARY KEY (id)
                    )
                    """;

            Statement statement = connection.createStatement();
            statement.execute(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I query records from a table?

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class JdbcQueryExample {
    // Database connection information
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        // Get a connection to database.
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            // Create a statement object.
            Statement statement = connection.createStatement();

            // Executes a query command to select isbn and the book title
            // from books table. The execute query returns a ResultSet
            // object which is the result of our query execution.
            String query = "SELECT isbn, title, published_year FROM book";
            ResultSet books = statement.executeQuery(query);

            // To get the value returned by the statement.executeQuery we
            // need to iterate the books object until the last items.
            while (books.next()) {
                // To get the value from the ResultSet object we can call
                // a method that correspond to the data type of the column
                // in database table. In the example below we call
                // books.getString("isbn") to get the book's ISBN 
                // information.
                System.out.println(books.getString("isbn") + ", " +
                        books.getString("title") + ", " +
                        books.getInt("published_year"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central

How do I insert a record into database table?

In this example you’ll learn how to create a program to insert data into a database table. To insert a data we need to get connected to a database. After a connection is obtained you can create a java.sql.Statement object from it, and using this object we can execute some query strings.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class InsertStatementExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Create a statement object.
            Statement stmt = connection.createStatement();
            String sql = "INSERT INTO book (isbn, title, published_year) " +
                    "VALUES ('978-1617293566', 'Modern Java in Action', 2019)";

            // Call execute() method of the statement object and pass the
            // query.
            stmt.execute(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Below is the script from creating the book table.

CREATE TABLE `book`
(
    `id`             bigint(20) unsigned                  NOT NULL AUTO_INCREMENT,
    `isbn`           varchar(50) COLLATE utf8_unicode_ci  NOT NULL,
    `title`          varchar(100) COLLATE utf8_unicode_ci NOT NULL,
    `published_year` int(11)                                       DEFAULT NULL,
    `price`          decimal(10, 2)                       NOT NULL DEFAULT '0.00',
    PRIMARY KEY (`id`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8
  COLLATE = utf8_unicode_ci;

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

Maven Central