Java Mysql 简明教程
Java & MySQL - Select Records Example
本章提供了一个示例,说明如何使用 JDBC 应用程序从表中选择/提取记录。在执行以下示例之前,确保您已准备就绪 −
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 −
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To execute the following example you can replace the username and password with your actual user name and password.
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Your MySQL database you are using is up and running.
Required Steps
创建新的数据库使用 JDBC 应用程序需要执行以下步骤:
The following steps are required to create a new Database using JDBC application −
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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.
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Open a connection − Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.
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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.
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Extract Data − Once SQL query is executed, you can fetch records from the table.
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Clean up the environment − try with resources automatically closes the resources.
Sample Code
将以下示例复制并粘贴到 TestApplication.java 中,如下进行编译和运行:
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();
}
}
}
现在让我们如下编译上述示例:
Now let us compile the above example as follows −
C:\>javac TestApplication.java
C:\>
运行 TestApplication 时,它会生成以下结果:
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:\>