Java Mysql 简明教程

Java & MySQL - LIKE Clause Example

本章提供了使用 JDBC 应用程序从表中选择记录的示例。这将在从表中选择记录时使用 LIKE 子句添加其他条件。在执行以下示例之前，确保您已执行以下操作：

This chapter provides an example on how to select records from a table using JDBC application. This would add additional conditions using LIKE 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

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 −

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 fetch records from a table which meet given condition. This Query makes use of LIKE clause to select records to select all the students whose first name starts with "za".
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();) {
         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 first LIKE '%za%'";
         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();
      }
   }
}

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
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: 100, Age: 30, First: Zara, Last: Ali
ID: 102, Age: 30, First: Zaid, Last: Khan
C:\>