Java中JDBC连接数据库步骤 以及 Statement和preparseStatement

1.prepareStatement可以替换变量

在SQL语句中可以包含?，可以用

    ps=conn.prepareStatement("select * from Cust where ID=?");

    int sid=1001;

    ps.setInt(1, sid);

    rs = ps.executeQuery();

可以把?替换成变量。

 

2.Statement只能用

    int sid=1001;

    Statement stmt = conn.createStatement();

    ResultSet rs = stmt.executeQuery("select * from Cust where ID="+sid);

来实现

 

3.PrepareStatement是欲编译方式执行SQL，多次调用此连接时，速度要比Statement快，所以建议用PrepareStatement

例子如下：

 

下面的程序都有注释，你应该能看懂了！ import java.sql.*; public class UsePreparedStatement {         public static void main(String[] args) {                 String url = "jdbc:mysql://localhost/sql_test";                 String userName = "root";                 String password = "root";                 Connection conn = null;                 try {                          //1.加载驱动                         Class.forName("com.mysql.jdbc.Driver");                 } catch(ClassNotFoundException e) {                         System.out.println("加载驱动器类时出现异常");                 }                                  try {                         //2.获取连接                         conn = DriverManager.getConnection(url, userName, password);                                                  //3.创建PreparedStatement语句                         PreparedStatement pstmtDelete = conn.prepareStatement(                                         "DELETE FROM student WHERE stu_id>=?");                                         PreparedStatement pstmtInsert = conn.prepareStatement(                                         "INSERT INTO student VALUES(?, ?, ?, ?)");                                 PreparedStatement pstmtSelect = conn.prepareStatement(                                         "SELECT * FROM student WHERE stu_id>=? " +                                         "ORDER BY stu_id");                                                  int id = 15;                                                  //使用setXXX方法设置IN参数                         pstmtSelect.setString(1, Integer.toString(id));                                                  //多次执行同一语句                         for (int i=0; i<3; i++, id++) {                                                  //4.使用setXXX方法设置IN参数                                 pstmtDelete.setString(1, Integer.toString(id));                                                                  pstmtInsert.setString(1, Integer.toString(id));                                 pstmtInsert.setString(2, "name"+id);                                 pstmtInsert.setString(3, "city"+id);                                 pstmtInsert.setDate(4, new Date(78, 2, id));                                                  //5.执行PreparedStatement语句                                 pstmtDelete.executeUpdate();                                 pstmtInsert.executeUpdate();                                 ResultSet rs = pstmtSelect.executeQuery();                                                                  System.out.println("");                                 System.out.println("第 " + (i+1) + " 次循环后的结果集为：");                                                  //显示返回的结果集                                 while (rs.next()) {                                         String stuID      = rs.getString(1);                                         String name    = rs.getString(2);                                         String address = rs.getString(3);                                         String birthday= rs.getString(4);                                         System.out.println(stuID + "   " +                                                         name + "   " + address + "   " + birthday);                                 }                         }                                                  pstmtDelete.close();                         pstmtInsert.close();                         pstmtSelect.close();                                          } catch(SQLException e) {                         System.out.println("出现SQLException异常");                 } finally {                         //6.关闭语句和数据库连接                         try {                                 if (conn != null) conn.close();                         } catch(SQLException e) {                                 System.out.println("关闭数据库连接时出现异常");                         }                                 }                          } }