package datepaseConnect;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class Select {
    public static void main(String[] args) {
        
    Connection conn=null;
    Statement stm =null;
    ResultSet res=null;
    try {
        //获取数据库连接
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        System.out.println("数据库驱动加载成功");
        String url="jdbc:sqlserver://localhost:1433;DatabaseName=BDQN_1";
        String username="sa";
        String password="qaz123";
        conn=DriverManager.getConnection(url, username, password);
        System.out.println("数据库连接成功");
        //建立数据库通道
        stm=conn.createStatement();
        //声明要执行的sql语句
        String sql="SELECT KC.kechengcode,KC.kechengname,KC.kechengcontent,CL.classname " +
                "FROM kecheng AS KC INNER JOIN classinfo AS CL" +
                "ON CL.classid=KC.classid ";
               
               
        //获取查询结果集
        res=stm.executeQuery(sql);
        //使用while循环遍历结果集
        while(res.next()){
            System.out.print(res.getString("kechengcode"));
            System.out.print(res.getString("kechengname"));
            System.out.println(res.getString("kechengcontent"));
            System.out.println(res.getString("classname"));
        }
    } catch (Exception e) {
        
        e.printStackTrace();
    }
     try {
         res.close();
         stm.close();
         conn.close();
        
    } catch (Exception e) {
        
        e.printStackTrace();
    }

报告的异常信息:


数据库驱动加载成功
数据库连接成功
com.microsoft.sqlserver.jdbc.SQLServerException: 'CL' 附近有语法错误。
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(SQLServerException.java:216)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.getNextResult(SQLServerStatement.java:1515)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.doExecuteStatement(SQLServerStatement.java:792)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement$StmtExecCmd.doExecute(SQLServerStatement.java:689)
    at com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:5696)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1715)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeCommand(SQLServerStatement.java:180)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeStatement(SQLServerStatement.java:155)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeQuery(SQLServerStatement.java:616)
    at datepaseConnect.Select.main(Select.java:31)
java.lang.NullPointerException
    at datepaseConnect.Select.main(Select.java:48)
     
}

}

还真是啊,谢谢了啊,分数全部给你哈