java mysql 增删改查

1. Java MySQL插入数据

要将数据插入MySQL数据库，可以使用Java JDBC API的executeUpdate()方法。以下是一个简单的Java程序，可以将数据插入数据库：

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

public class InsertData {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            // Open a connection
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "root", "");

            // Execute a query
            System.out.println("Inserting records into the table...");
            stmt = conn.createStatement();

            String sql = "INSERT INTO students (id, name, age) VALUES (1001, 'John Smith', 20)";
            stmt.executeUpdate(sql);

            System.out.println("Records inserted successfully...");
        } catch (SQLException se) {
            // Handle errors for JDBC
            se.printStackTrace();
        } catch (Exception e) {
            // Handle errors for Class.forName
            e.printStackTrace();
        } finally {
            // finally block used to close resources
            try {
                if (stmt != null) {
                    conn.close();
                }
            } catch (SQLException se) {
            } // do nothing
            try {
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException se) {
                se.printStackTrace();
            } // end finally try
        } // end try
    }
}

2. Java MySQL更新数据

要更新MySQL数据库中的数据，可以使用Java JDBC API的executeUpdate()方法。以下是一个简单的Java程序，可以更新数据库中的数据：

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

public class UpdateData {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            // Open a connection
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "root", "");

            // Execute a query
            System.out.println("Updating records in the table...");
            stmt = conn.createStatement();

            String sql = "UPDATE students SET age = 21 WHERE id = 1001";
            stmt.executeUpdate(sql);

            System.out.println("Records updated successfully...");
        } catch (SQLException se) {
            // Handle errors for JDBC
            se.printStackTrace();
        } catch (Exception e) {
            // Handle errors for Class.forName
            e.printStackTrace();
        } finally {
            // finally block used to close resources
            try {
                if (stmt != null) {
                    conn.close();
                }
            } catch (SQLException se) {
            } // do nothing
            try {
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException se) {
                se.printStackTrace();
            } // end finally try
        } // end try
    }
}

3. Java MySQL删除数据

要从MySQL数据库中删除数据，可以使用Java JDBC API的executeUpdate()方法。以下是一个简单的Java程序，可以删除数据库中的数据：

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

public class DeleteData {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            // Open a connection
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "root", "");

            // Execute a query
            System.out.println("Deleting records from the table...");
            stmt = conn.createStatement();

            String sql = "DELETE FROM students WHERE id = 1001";
            stmt.executeUpdate(sql);

            System.out.println("Records deleted successfully...");
        } catch (SQLException se) {
            // Handle errors for JDBC
            se.printStackTrace();
        } catch (Exception e) {
            // Handle errors for Class.forName
            e.printStackTrace();
        } finally {
            // finally block used to close resources
            try {
                if (stmt != null) {
                    conn.close();
                }
            } catch (SQLException se) {
            } // do nothing
            try {
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException se) {
                se.printStackTrace();
            } // end finally try
        } // end try
    }
}

4. Java MySQL查询数据

要从MySQL数据库中查询数据，可以使用Java JDBC API的executeQuery()方法。以下是一个简单的Java程序，可以查询数据库中的数据：

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

public class SelectData {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            // Open a connection
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "root", "");

            // Execute a query
            System.out.println("Creating statement...");
            stmt = conn.createStatement();

            String sql = "SELECT id, name, age FROM students";
            ResultSet rs = stmt.executeQuery(sql);

            // Extract data from result set
            while (rs.next()) {
                // Retrieve by column name
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");

                // Display values
                System.out.print("ID: " + id);
                System.out.print(", Name: " + name);
                System.out.println(", Age: " + age);
            }
            rs.close();
            System.out.println("Records selected successfully...");
        } catch (SQLException se) {
            // Handle errors for JDBC
            se.printStackTrace();
        } catch (Exception e) {
            // Handle errors for Class.forName
            e.printStackTrace();
        } finally {
            // finally block used to close resources
            try {
                if (stmt != null) {
                    conn.close();
                }
            } catch (SQLException se) {
            } // do nothing
            try {
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException se) {
                se.printStackTrace();
            } // end finally try
        } // end try
    }
}