读数据库

Question

String sql="select * from information";
ResultSet rs1=stmt.executeQuery(sql);
while(rs1.next())
{
    String sname=rs1.getString("sname");
    String tname=rs1.getString("tname");
     log.info(sname+"----------------");
     log.info(tname+"----------------");
    
    String sql1="select * from teacher where tname='"+tname+"'";
     ResultSet rs2=stmt.executeQuery(sql1);
     log.info(rs2.getString("xueyuan"));
}我这样写对不对？log.info(rs2.getString("xueyuan"));为什么读不出来？

Answer 1

要先执行rs.next()
while(rs.next())
      log.info(rs2.getString("xueyuan")); 

Answer 2

上面代码修改为：String sql="select * from information"; 
ResultSet rs1=stmt.executeQuery(sql); 
while(rs1.next()) 
{ 
  String sname=rs1.getString("sname"); 
  String tname=rs1.getString("tname"); 
    log.info(sname+"----------------"); 
    log.info(tname+"----------------"); 
    
  String sql1="select * from teacher where tname='"+tname+"'"; 
    
    ResultSet rs2=stmt.executeQuery(sql1); 
    
    while(rs2.next())
        log.info(rs2.getString("xueyuan")); 
} 

Answer 3

上面代码修改为：String sql="select * from information"; 
ResultSet rs1=stmt.executeQuery(sql); 
while(rs1.next()) 
{ 
  String sname=rs1.getString("sname"); 
  String tname=rs1.getString("tname"); 
    log.info(sname+"----------------"); 
    log.info(tname+"----------------"); 
    
  String sql1="select * from teacher where tname='"+tname+"'"; 
    
    ResultSet rs2=stmt.executeQuery(sql1); 
    
    while(rs2.next())
        log.info(rs2.getString("xueyuan")); 
} 

Answer 4

不好意思，怎么发了两次啊！注意，最后别忘记关闭rs1,rs2和数据库连接