JDBC预编译statement（preparedstatement）和statement的比较、execute与executeUpdate的区别

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
    
public class TestJDBC {
    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
  
        String sql = "insert into hero values(null,?,?,?)";
        try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8","root", "admin");
            // 根据sql语句创建PreparedStatement
            PreparedStatement ps = c.prepareStatement(sql);
        ) {
             
            // 设置参数
            ps.setString(1, "提莫");
            ps.setFloat(2, 313.0f);
            ps.setInt(3, 50);
            // 执行
            ps.execute();
  
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    
    }
}

String sql = "insert into hero values(null,"+"‘提莫‘"+","+313.0f+","+50+")";

String sql = "insert into hero values(null,?,?,?)";

public class TestJDBC {
    public static void main(String[] args) {
  
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
  
        String sql = "insert into hero values(null,?,?,?)";
        try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8","root", "admin"); 
            Statement s = c.createStatement(); 
            PreparedStatement ps = c.prepareStatement(sql);
        ) {
            // Statement需要进行字符串拼接，可读性和维修性比较差
            String sql0 = "insert into hero values(null," + "‘提莫‘" + "," + 313.0f + "," + 50 + ")";
            s.execute(sql0);
  
            // PreparedStatement 使用参数设置，可读性好，不易犯错
            // "insert into hero values(null,?,?,?)";
            ps.setString(1, "提莫");
            ps.setFloat(2, 313.0f);
            ps.setInt(3, 50);
            ps.execute();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
  
    }
}

public class TestJDBC {
    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
 
        try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8","root", "admin");
            Statement s = c.createStatement();) {
 
            String sqlInsert = "insert into Hero values (null,‘盖伦‘,616,100)";
            String sqlDelete = "delete from Hero where id = 100";
            String sqlUpdate = "update Hero set hp = 300 where id = 100";
 
            // 相同点：都可以执行增加，删除，修改
 
            s.execute(sqlInsert);
            s.execute(sqlDelete);
            s.execute(sqlUpdate);
            s.executeUpdate(sqlInsert);
            s.executeUpdate(sqlDelete);
            s.executeUpdate(sqlUpdate);
 
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
 
    }
}

public class TestJDBC {
    public static void main(String[] args) {
  
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
 
        try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8","root", "admin");
            Statement s = c.createStatement();) {
  
            // 不同1：execute可以执行查询语句
            // 然后通过getResultSet，把结果集取出来
            String sqlSelect = "select * from hero";
  
            s.execute(sqlSelect);
            ResultSet rs = s.getResultSet();
            while (rs.next()) {
                System.out.println(rs.getInt("id"));
            }
  
            // executeUpdate不能执行查询语句
            // s.executeUpdate(sqlSelect);
  
            // 不同2:
            // execute返回boolean类型，true表示执行的是查询语句，false表示执行的是insert,delete,update等等
            boolean isSelect = s.execute(sqlSelect);
            System.out.println(isSelect);
  
            // executeUpdate返回的是int，表示有多少条数据受到了影响
            String sqlUpdate = "update Hero set hp = 300 where id < 100";
            int number = s.executeUpdate(sqlUpdate);
            System.out.println(number);
  
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
  
    }
}