一、execute()

execute()：几乎可以执行任何SQL语句，返回值是boolean值，表明该SQL语句是否返回ResultSet对象

boolean值：

true：使用getResultSet()方法获取返回的ResultSet对象 false：使用getUpdateCount()方法获取返回所影响的行数

import java.sql.*;
public class TestDemo {

public static void main(String[] args) {

	JDBCDemo jdbc = new JDBCDemo();
	}
}
		
class JDBCDemo{
    public JDBCDemo() {
    			
				try {
					//  1.
	    			Class.forName("com.mysql.cj.jdbc.Driver");

	    			//	2.
	    			Connection con = DriverManager.getConnection(
	    			"jdbc:mysql://localhost:3306/de?characterEncoding=gb2312&serverTimezone=UTC&useSSL=false", "root", "root");

	    			//	3.
	    			 Statement stmt = con.createStatement();
	    			 
	    			//	4.
	    			String sql = "SELECT * FROM tb_student";    //  sql语句
	     			Boolean bool = stmt.execute(sql); 
	     			System.out.println("bool = " + bool);
	     			if (bool) {
						ResultSet rs = stmt.getResultSet();		//	获取ResultSet对象
					//	5.
		     			while(rs.next()){
		     			   int studentNo = rs.getInt(1); // 指定第几列 
		     			   String studentName = rs.getString("studentName"); // 指定列名称
		     			   System.out.println(studentNo + "---" + studentName);
		     			}
		     			
		     		//  6.
		     			rs.close();
		     			stmt.close();
		     			con.close();
					}
				} catch (SQLException | ClassNotFoundException e) {
					e.printStackTrace();
				}
    }
}

二、executeUpdate

executeUpdate()：用于执行DDL和DML语句，返回值为所影响的行数

executeUpdate增强版（Java8新增）：executeLargeUpdate()，返回值为long类型，适用于DML语句的记录超过Interger.MAX_VALUES的情况

import java.sql.*;
public class TestDemo {

public static void main(String[] args) throws ClassNotFoundException, SQLException {

	JDBCDemo jdbc = new JDBCDemo();
	}
}
		
class JDBCDemo{
    public JDBCDemo() throws SQLException, ClassNotFoundException {
    		
					//  1.
	    			Class.forName("com.mysql.cj.jdbc.Driver");

	    			//	2.
	    			Connection con = DriverManager.getConnection(
	    			"jdbc:mysql://localhost:3306/de?characterEncoding=gb2312&serverTimezone=UTC&useSSL=false", "root", "root");

	    			//	3.
	    			 Statement stmt = con.createStatement();
	    			 
	    			//	4.
	    			String sql = "UPDATE tb_student SET studentName=狗蛋 WHERE studentNo=2013110101";   //  sql语句
	     			int res = stmt.executeUpdate(sql); 
	     		
	     			//	5.
	     			System.out.println( "所影响的记录行数：" + res );
		     	
		     			
		     		//  6
		     		stmt.close();
		     		con.close();
    }
				
}