求大神帮我看看，是哪里出了问题，谢谢（第一次运行成功了，第二次就报错了）

[sonwing_for]

Thu Jan 07 15:58:23 CST 2016 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'student' already exists
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
at com.mysql.jdbc.Util.getInstance(Util.java:387)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:939)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2478)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2547)
at com.mysql.jdbc.StatementImpl.executeUpdateInternal(StatementImpl.java:1541)
at com.mysql.jdbc.StatementImpl.executeLargeUpdate(StatementImpl.java:2605)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1469)
at Connection04.main(Connection04.java:30)
com.mysql.jdbc.JDBC4Connection@62937c


程序代码：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Connection04{

public static final String DEDRIVER = "org.gjt.mm.mysql.Driver";
public static void main(String [] args)throws Exception{

final String DBURL = "jdbc:mysql://localhost:3306/mldn";
final String DBUSER = "root";
final String DBPASS = "";
Connection conn = null;
String sql;
try{
Class.forName(DEDRIVER);//装载JDBC


}catch(ClassNotFoundException e){
e.printStackTrace();

}
try{

conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS);//建立连接
Statement stmt = conn.createStatement();//创建Statement对象,此对象是发送SQL语句的容器。将SQL语句发送到数据库系统中执行
sql = "create table student(NO char(20),name varchar(20),primary key(NO))";

int result = stmt.executeUpdate(sql);
if (result != -1) {
System.out.println("创建数据表成功");
sql = "insert into student(NO,name) values('2012001',张伟基)";
result = stmt.executeUpdate(sql);
sql = "insert into student(NO,name) values('2012002',周小俊)";
result = stmt.executeUpdate(sql);
sql = "select * from student";
ResultSet rs = stmt.executeQuery(sql);// executeQuery会返回结果的集合，否则返回空值
System.out.println("学号\t姓名");
while (rs.next()) {
System.out
.println(rs.getString(1) + "\t" + rs.getString(2));// 入如果返回的是int类型可以用getInt()
}

}
}catch(SQLException e){
e.printStackTrace();
}
System.out.println(conn);
try{
conn.close();
}catch(SQLException e){
e.printStackTrace();
}
}
}

[海中跳到鱼]

student 这个表第一次已经创建完成,应该判断下表是否创建,若创建则跳过,否则创建

[心随自在飞]

重复创建了，数据库就报错了呀！

[北极熊丶]

这错误都明显摆着了： com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'student' already exists

[g149327]

sql = "create table student(NO char(20),name varchar(20),primary key(NO))"; 改为 CREATE or REPLACE table student(NO char(20),name varchar(20),primary key(NO))";

[tiaoxixiaoji]

student表已经存在，sql = "create table student(NO char(20),name varchar(20),primary key(NO))";这条语句被重复执行

[glzmzd]

sql="DROP TABLE IF EXISTS `studeng`" 加上这么一句应该OK。

[dai_mo]

引用 3 楼 gjh1328714985 的回复:

这错误都明显摆着了： com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'student' already exists

.

[Usher丶AckMan]

重复建表了 在第一个sql中加上DROP TABLE IF EXISTS TABLEName,然后再创建..