java.sql.SQLException: Can not issue empty query.

1、错误描述

java.sql.SQLException: Can not issue empty query.at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:996)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:935)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:924)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:870)at com.mysql.jdbc.StatementImpl.checkNullOrEmptyQuery(StatementImpl.java:492)at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1367)at com.you.sql.Student.queryStudent(Student.java:51)at com.you.sql.Student.main(Student.java:79)

2、错误原因

/** * * @Project:MySQL * @Title:Student.java * @Package:com.you.sql * @Description: * @Author:YouHaiDong * @Date:2015年6月10日 下午11:49:36 * @Version: */package com.you.sql;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;/** * <p>请用一句话概括功能</p> * @ClassName:Student * @Description: * @Author:YouHaiDong * @Date:2015年6月10日 下午11:49:36 * */public class Student{/** * 查询学生基本信息 * @Title:Student * @Description: * @Date:2015年6月11日 上午12:06:40 * @return :void * @throws */public static void queryStudent(){StringBuffer sql = new StringBuffer();String url = "jdbc:mysql://localhost:3333/student";String user = "root";String password = "root";Connection conn = null;Statement stat = null;ResultSet rs = null;try{conn = DriverManager.getConnection(url, user, password);stat = conn.createStatement();rs = stat.executeQuery(sql.toString());while(rs.next()){String stuId = rs.getString("stu_id");String stuName = rs.getString("stu_name");String stuSex = rs.getString("sex");String stuAge = rs.getString("stu_age");String stuPhone = rs.getString("stu_phone");System.out.println("学号："+stuId+"----"+"姓名："+stuName+"----"+"性别："+stuSex+"---"+"年龄："+stuAge+"----"+"电话："+stuPhone);}}catch (SQLException e){e.printStackTrace();}}/** * * @Title:Student * @Description: * @param args * @Date:2015年6月11日 上午12:07:53 * @return :void * @throws */public static void main(String args[]){queryStudent();}}

3、解决办法

由于在执行rs = stat.executeQuery(sql.toString());时，sql为空，导致报错

StringBuffer sql = new StringBuffer();

    sql.append("select * from t_stu_info ");