Java sql update пример

A Java MySQL UPDATE example

Java MySQL FAQ: Can you share an example of a Java MySQL UPDATE example (using a Java PreparedStatement object)?

Sure. I just worked up a Java MySQL UPDATE example, using the Java PreparedStatement class, and a sample MySQL database table we can work with.

A simple MySQL database table

The first thing we need for our Java UPDATE example is a sample MySQL database table. To keep it simple — but also show several different data types — I’ve created the following MySQL database table:

create table users ( id int unsigned auto_increment not null, first_name varchar(32) not null, last_name varchar(32) not null, date_created timestamp default now(), is_admin boolean, num_points int, primary key (id) ); -- insert some sample records insert into users (first_name, last_name) values ('Fred', 'Flinstone'); insert into users (first_name, last_name) values ('Barney', 'Rubble');

A few of these fields are a little contrived, but I wanted to show several different data types in one table, so this is what I came up with. In particular, the field num_points is a little unusual, but I made it up so I could show an int data type in this table, and I was thinking of those websites where points are awarded for giving correct answers.

Other than that, this MySQL database table is relatively normal, though it is greatly simplified.

A Java MySQL UPDATE PreparedStatement example

Given that MySQL database table design, let’s assume that we just want to update one record in this table. To do so, we just need to follow these steps:

1. Create a Java Connection to our MySQL database.
2. Create a SQL UPDATE statement, using the Java PreparedStatement syntax.
3. Set the fields on our Java PreparedStatement object.
4. Execute a Java PreparedStatement .
5. Close our Java database connection.
6. Catch any exceptions that may come up during the process.

I’ve tried to document the following Java MySQL UPDATE example so you can see these steps. Note that in this example my MySQL database username is «root», my password is blank, and the MySQL database is running on the same computer where this program is run, so the database host name is «localhost».

import java.sql.*; /** * A Java MySQL UPDATE example. * Demonstrates the use of a SQL UPDATE statement against a * MySQL database, called from a Java program. * * Created by Alvin Alexander, http://devdaily.com * */ public class JavaMysqlPreparedStatementUpdateExample < public static void main(String[] args) < try < // create a java mysql database connection String myDriver = "org.gjt.mm.mysql.Driver"; String myUrl = "jdbc:mysql://localhost/test"; Class.forName(myDriver); Connection conn = DriverManager.getConnection(myUrl, "root", ""); // create the java mysql update preparedstatement String query = "update users set num_points = ? where first_name = ?"; PreparedStatement preparedStmt = conn.prepareStatement(query); preparedStmt.setInt (1, 6000); preparedStmt.setString(2, "Fred"); // execute the java preparedstatement preparedStmt.executeUpdate(); conn.close(); >catch (Exception e) < System.err.println("Got an exception! "); System.err.println(e.getMessage()); >> >

Note that this SQL UPDATE query is a little unusual, but not totally uncommon. Typically in a database program like this you’ll end up updating rows based on the primary key of the database table. Specifically, in this example, you’d probably already know the «id» for the user Fred, and when you go to update Fred’s data, you would normally do it like this:

update users set num_points = 6000 where >but because this is a sample program, I decided to show the query this way.

Java MySQL UPDATE example — results

After this Java MySQL UPDATE query runs, you can verify that it worked by looking at the data from the MySQL command prompt, running a SELECT query like this:

where you will see some output like this:

+----+------------+-----------+---------------------+----------+------------+ | id | first_name | last_name | date_created | is_admin | num_points | +----+------------+-----------+---------------------+----------+------------+ | 2 | Fred | Flinstone | 2010-06-23 14:02:00 | 0 | 6000 | +----+------------+-----------+---------------------+----------+------------+ 1 row in set (0.00 sec)

Java MySQL UPDATE example using PreparedStatement — summary

In «real world» Java database programs I almost always use the Spring JDBC libraries to access a database, but when you’re first getting started, or working on small programs, I think it’s important to see examples like this so you can understand how things work under the covers.

In summary, this example demonstrated:

1. How to connect to a MySQL database.
2. How to write a MySQL UPDATE query for use with a PreparedStatement .
3. How to set the field values for a PreparedStatement .
4. How to execute the Java PreparedStatement .
5. How to close the MySQL database connection.
6. One way to confirm that our data was successfully updated in our MySQL database.

I hope this Java MySQL UPDATE example (using a Java PreparedStatement ) makes sense. As usual, if you have any questions or comments about this example, just use the Comment form below.

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Java sql update пример

Для добавления, редактирования и удаления данных мы можем ипользовать рассмотренный в прошлой теме метод executeUpdate . С помощью результата метода мы можем проконтроллировать, сколько строк было добавлено, изменено или удалено.

Добавление

Так, возьмем созданную в прошлой теме таблицу Products:

CREATE TABLE Products ( Id INT PRIMARY KEY AUTO_INCREMENT, ProductName VARCHAR(20), Price INT )

И добавим в эту таблицу несколько объектов:

import java.sql.*; public class Program < public static void main(String[] args) < try< String url = "jdbc:mysql://localhost/store?serverTimezone=Europe/Moscow&useSSL=false"; String username = "root"; String password = "password"; Class.forName("com.mysql.cj.jdbc.Driver").getDeclaredConstructor().newInstance(); try (Connection conn = DriverManager.getConnection(url, username, password))< Statement statement = conn.createStatement(); int rows = statement.executeUpdate("INSERT Products(ProductName, Price) VALUES ('iPhone X', 76000)," + "('Galaxy S9', 45000), ('Nokia 9', 36000)"); System.out.printf("Added %d rows", rows); >> catch(Exception ex) < System.out.println("Connection failed. "); System.out.println(ex); >> >

Для добавления данных в БД применяется команда INSERT. В данном случае в таблицу Products добавляется три объекта. И после выполнения программы на консоли мы увидим число добавленных объектов:

C:\Java>javac Program.java C:\Java>java -classpath c:\Java\mysql-connector-java-8.0.11.jar;c:\Java Program Added 3 rows C:\Java>

А добавленные строки мы можем увидеть в таблице в бд MySQL:

Редактирование

Изменим строки в таблице, например, уменьшим цену товара на 5000 единиц. Для изменения применяется команда UPDATE:

import java.sql.*; public class Program < public static void main(String[] args) < try< String url = "jdbc:mysql://localhost/store?serverTimezone=Europe/Moscow&useSSL=false"; String username = "root"; String password = "password"; Class.forName("com.mysql.cj.jdbc.Driver").getDeclaredConstructor().newInstance(); try (Connection conn = DriverManager.getConnection(url, username, password))< Statement statement = conn.createStatement(); int rows = statement.executeUpdate("UPDATE Products SET Price = Price - 5000"); System.out.printf("Updated %d rows", rows); >> catch(Exception ex) < System.out.println("Connection failed. "); System.out.println(ex); >> >

Удаление

Удалим один объект из таблицы с помощью команды DELETE:

import java.sql.*; public class Program < public static void main(String[] args) < try< String url = "jdbc:mysql://localhost/store?serverTimezone=Europe/Moscow&useSSL=false"; String username = "root"; String password = "password"; Class.forName("com.mysql.cj.jdbc.Driver").getDeclaredConstructor().newInstance(); try (Connection conn = DriverManager.getConnection(url, username, password))< Statement statement = conn.createStatement(); int rows = statement.executeUpdate("DELETE FROM Products WHERE row(s) deleted", rows); >> catch(Exception ex) < System.out.println("Connection failed. "); System.out.println(ex); >> >

Как видно из примеров, не так сложно взаимодействовать с базой данных. Достаточно передать в метод executeUpdate нужную команду SQL.

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UPDATE records in a table with JDBC

The JDBC classes and interfaces are available in java.sql and javax.sql packages.

Steps to update records in a table with UPDATE SQL statement using JDBC —

Class.forName("oracle.jdbc.driver.OracleDriver");

In the upcoming example, we are going to create a table within the Oracle database using its JDBC driver.

Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE","scott", "tiger");

• 1521 is the general port number to connect to the database.
• XE stands for Oracle Express Edition Database.
• scott is our username to connect to the Oracle database and tiger is the password.

Statement stmt = con.createStatement();

Creating a Statement object to using createStatement() method of Connection interface.

int count = stmt.executeUpdate(query);

count gives us the total number of rows updated in a database table due to the execution of a SQL query using executeUpdate() method, where query is a String object which specifies the SQL query to execute.

con is a Connection reference used to close the connection with the database after the updation is over.

Updating data in database table using JDBC

 import java.sql.*; class A < public static void main(String. ar) < try < //First SQL UPDATE Query to update record. String query1 = "Update MyTable2 Set FirstName='Thomas' Where FirstName = 'Tom'"; //Second SQL UPDATE Query to update record. String query2 = "Update MyTable2 Set FirstName='Bradly' where age = '53'"; //Third SQL SELECT Query to retrieve updated records. String query3 = "SELECT * FROM MyTable2"; Class.forName("oracle.jdbc.driver.OracleDriver"); Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE","System", "Promila21"); Statement stmt = con.createStatement(); //Executing first SQL UPDATE query using executeUpdate() method of Statement object. int count = stmt.executeUpdate(query1); System.out.println("Number of rows updated by executing query1 = " + count); //Executing second SQL UPDATE query using executeUpdate() method of Statement object. count = stmt.executeUpdate(query2); System.out.println("Number of rows updated by executing query2 = " + count); //Executing SQL SELECT query using executeQuery() method of Statement object. ResultSet rs = stmt.executeQuery(query3); System.out.println("Result of executing query3 to display updated records"); System.out.println("ID " + "\t" + "FirstName" + "\t" + "LastName" + "\t" + "Age"); //looping through the number of row/rows retrieved after executing SELECT query3 while(rs.next()) < System.out.print(rs.getString("ID") + "\t"); System.out.print(rs.getString("FirstName") + "\t" + "\t"); System.out.print(rs.getString("LastName")+ "\t" + "\t"); System.out.println(rs.getString("Age") + "\t"); >> catch(SQLException e) < System.out.println(e); >>//main() method ends >//class definitin ends 

Output

Number of rows updated by executing query1 = 1 Number of rows updated by executing query2 = 1 Result of executing query3 to display updated records ID FirstName LastName Age 1 Thomas Hanks 61 2 Johnny Depp 54 3 Bradly Pitt 53

In the output, you may see the updated records in table MyTable, where FirstName Tom is changed to Thomas and Brad is changed to Bradley.

ID	FirstName	LastName	Age
1	Thomas	Hanks	61
2	Johnny	Depp	54
3	Bradley	Pitt	53

Table — MyTable

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